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STOCK OPTION PLAN AND WARRANTS, STOCK OPTIONS (Details) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Stock option fair value assumptions [Abstract]    
Stock based compensation expense $ 935,097us-gaap_ShareBasedCompensation $ 2,318,355us-gaap_ShareBasedCompensation
Maximum [Member]    
Stock option fair value assumptions [Abstract]    
Weighted average fair value per option granted (in dollars per share) $ 0.50ztho_WeightedAverageFairValuePerOptionGranted
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
 
Minimum [Member]    
Stock option fair value assumptions [Abstract]    
Weighted average fair value per option granted (in dollars per share) $ 0.31ztho_WeightedAverageFairValuePerOptionGranted
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
 
Stock Options [Member]    
Number of shares [Roll Forward]    
Outstanding at beginning of period (in shares) 9,583,762us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
7,728,877us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Granted (in shares) 2,372,800us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
2,176,535us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Exercised (in shares) 0us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
(293,650)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Expired and Cancelled (in shares) (922,887)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
(28,000)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Outstanding at end of period (in shares) 11,033,675us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
9,583,762us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Exercisable at the end of the period (in shares) 11,033,675us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
9,536,262us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Weighted average exercise price [Roll Forward]    
Outstanding at the beginning of period (in dollars per share) $ 1.16us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
$ 1.01us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Granted (in dollars per share) $ 0.58us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
$ 1.67us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Exercised (in dollars per share) $ 0us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
$ 0.98us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Expired and Cancelled (in dollars per share) $ 0.99us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
$ 2.18us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Outstanding at end of period (in dollars per share) $ 1.05us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
$ 1.16us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Exercisable at end of the period (in dollars per share) $ 1.05us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
$ 1.17us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Additional Disclosures [Abstract]    
Aggregate intrinsic value 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
 
Weighted average remaining contractual term 2 years 3 months 18 days  
Stock option fair value assumptions [Abstract]    
Weighted average fair value per option granted (in dollars per share)   $ 1.04ztho_WeightedAverageFairValuePerOptionGranted
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Risk free interest rate minimum (in hundredths) 0.86%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
0.65%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Risk free interest rate maximum (in hundredths) 1.75%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
0.81%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Expected dividend yield (in hundredths) 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Expected lives 2 years 8 months 8 days 2 years 8 months 10 days
Expected volatility rate minimum (in hundredths) 82.11%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
99.79%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Expected volatility rate maximum (in hundredths) 98.91%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
108.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Expiration from date of grant P5Y P5Y
Shares available for issuance under the Plan (in shares) 6,966,325us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
8,416,238us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Unrecognized stock based compensation to be recognized 22,103us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
77,595us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Stock Options [Member] | Employees [Member]    
Number of shares [Roll Forward]    
Granted (in shares) 2,372,800us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ ztho_GroupAxis
= ztho_EmployeesMember
2,176,535us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ ztho_GroupAxis
= ztho_EmployeesMember
Stock option fair value assumptions [Abstract]    
Stock based compensation expense $ 935,097us-gaap_ShareBasedCompensation
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ ztho_GroupAxis
= ztho_EmployeesMember
$ 2,318,355us-gaap_ShareBasedCompensation
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ ztho_GroupAxis
= ztho_EmployeesMember
Percentage of options that vested at grant date (in hundredths)   25.00%ztho_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfAwardsVestedAtGrantDate
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ ztho_GroupAxis
= ztho_EmployeesMember
Award vesting percentage on 90 days subsequent to the grant date (in hundredths)   25.00%ztho_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPercentageOnNinetyDaysSubsequentToGrantDatePercentage
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ ztho_GroupAxis
= ztho_EmployeesMember
Award vesting percentage on 180 days subsequent to the grant date (in hundredths)   25.00%ztho_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPercentageOnOneHundredAndEightyDaysSubsequentToGrantDatePercentage
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ ztho_GroupAxis
= ztho_EmployeesMember
Award vesting percentage on 270 days subsequent to the grant date (in hundredths)   25.00%ztho_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPercentageOnTwoHundredAndSeventyDaysSubsequentToGrantDatePercentage
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ ztho_GroupAxis
= ztho_EmployeesMember