I read about the ZZZZZZZZZZZZZZZZZZ name in a book on computer crime about 25 years ago. The book was very detailed and had names and details for all the perps and the dates of the crimes. Do you remember books, things made from paper that could be borrowed from libraries and bought in shops?
The Salami slicing rounding down is unique in computer since it is the only theft that can be performed on a computer, all the other Salami slicing frauds use computers as part of the system but are dependant on having a computer to do it, i.e. the fraud could just as easily be performed using a manual system.
Richard Pryor character also had access to the banks natural language interface for programming, 's funny how Hollywood thinks all programming languages are programmed in natural English.
The actual rounding down fraud would not be all that difficult to do in Cobol. It's also amazing how much money banks hold in dormant accounts and accounts that were supposed to be closed but were not closed because the account didn't have a zero balance.
Security controls are a lot better now that they were 30 years ago, and I have worked on systems where it was very easy to get a fix applied in a production environment after a problem occurred. And I have even had to recreate some programs where the original source code has been 'lost'. Very convenient if you've hard coded an account number in the interest calculation module!
IMHO the round down salami slice is entirely probable, FFS what bank is going to take a member of staff to court for theft and highlight to the world that their own internal security has failed.