In that case, why not just stop at the first zip and hash that? TorrentZip does state it uses "standard values", but I'm not sure how (nothing about the method seems mentioned).
IWith downloaded "ROMS" becoming clearly the majority of ROMS currently, something has to be out there eventually as a suggested standard. The days of dumping media storage are coming to an end slowly (at least half way there maybe?)
The below is faulted and ends in the obvious, but it's all I have now :-/....
Without knowing how compression works, the problem seems to be the directories. For the files one could just get the SHA (or whatever) of all files, sort those ascending and add them in that order to a container right? But the directories, unless they are only added in when each file requires them, I don't see a more unique way. But even then there would be the problem of identical files, which leads my brain to the problem of how to insert identical files with using just the directory tree as a reference. I could get an entire branched list, sort it with some method, then add them... which is back to the obvious, but which method? Some POSIX, UTF aware sort method would do, but which?