Final update for anyone who needs a similar solution. This is working for me now. I replaced the 'xxx'/'zxxxz' convention with &DASH& and &SLASH& since clean leaves & in place and I needed to put back in dashes and needed to insert a slash between artist and album. To me it is more readable and obvious, since I usually only find myself needing to tweak this at most once a year. Here is the full equation in place now:
If(IsEqual(FilePath(),\\ZEUS\Audio\iTunes Downloads, 8), [Filename], Replace(Replace(C:\Music\iTunes Library\Replace(Replace(Replace(Clean(Replace([Artist]&SLASH&[Album], -, &DASH&), 3), -, _), &DASH&, -), &SLASH&, \)\Replace(Replace([Filename (name)],.flac,.mp3),.ac3,.mp3),.\,\),\\,\))
As compared to:
If(IsEqual(FilePath(),\\ZEUS\Audio\iTunes Downloads, 8), [Filename], Replace(Replace(C:\Music\iTunes Library\Replace(Replace(Replace(Replace(Replace(Replace(Replace(Replace(Replace(Replace([Artist]|||[Album],<,_),>,_),:,_),",_),\,_),//,_),?,_),*,_),|||,\),|,_)\Replace(Replace([Filename (name)],.flac,.mp3),.ac3,.mp3),.\,\),\\,\))
Doesn't look much different by length but goes from 14 replaces to 8 replaces + 1 clean.
Thanks to MrC for helping fix the problem and come up with a cleaner solution.