If you’re trying to plate all three metals from one electrolyte this is tricky. Have a look at the electrochemical series copper is more noble than tin which is more noble than zinc. Therefore you need to use cheating agents to alter standard Electrode potentials to try and achieve co-deposition - if you want an alloy. I believe non-cyanide brass and bronze playing solutions are commercially available. Deposit composition depends on plating conditions.

if you’re trying to deposit single layers tin can be plated from acidic or alkaline baths as sulphate or sulphonate and stannate respectively.

I’m not sure but if you had poor adhesion you would expect tin to deposit onto your substrate and then fall off. Can you see ‘flakes’ of tin plate in your electrolyte? Have you tried using a copper substrate to check your electrolyte is working properly? Is the FTO coating compatible with the electrolyte? Does the electrical conductivity change before and after your plating experiments?

Have a look at this paper. It might help:

Jin, Hyunsoo & Park, Chansu & Park, Yoosei & Kim, Yangdo & Park, Sungkyun & Choi, Jongchan & Lee, Jae-Ho. (2016). Electrochemical studies on the CZT precursor deposition for CZTS solar cell application. Journal of the Korean Physical Society. 69. 1450-1455. 10.3938/jkps.69.1450.

Regards

John