Hey,
Your observations are correct, there is no ZZ available in FSB. And it is not possible to take an indi written in mq4 or other language and use it in FSB. For latter all indis must written in c#.

Standard ZZ has a problem - it recalculates its value if new high or low develops, therefore it is hard to backtest it correctly as the results will be overly optimistic, that is the reason why it is not available.