You may find that both spellings of TZCONVERTER and TZCONVERTOR are accepted by our parser. (notice the use of 'ER' vs 'OR')
TZCONVERTOR is native to TDV and documented in our manuals.
TZCONVERTER originates from our field-supported expansion pack formerly known from its Cisco vendor as "AS Utilities" or "AS Assets". You will find it in this path under the location you installed it: /PSAssets/Utilities/time/DateUtils/TZConverter
Their usage is identical. Unless you have a specified need for TZCONVERTER, you may find faster results with TZCONVERTOR since it is native and doesn't spawn additional processes when invoked.
To disable TZCONVERTER, go to the Studio's Custom Functions UI and de-select it from the list of functions. Afterwards, any use of it in a query will return this error: 'TZCONVERTER' is not a recognized function. On line <x> column <y> [parser-2909505]
Issue/Introduction
This discusses the syntax of date functions in Tibco Data Virtualization (TDV)