rec.games.int-fiction would be more appropriate (this group is about
writing games, that one is about playing them) but I don't think
anyone will sweat it.
My guess is that the ZIP program is written in such a way that it
tries to write a long integer to an unaligned memory address. This is
legal on 68020 and higher, but it crashes a 68000, so it's a common
problem with programs developed on newer machines. (I've made that
mistake.)
Unfortunately there's not much you can do unless you want to download
the code and debug it.
There's another Mac Z-code interpreter called "maczex" which
(hopefully) doesn't have the same bug. You can download that (from the
same place as ZIP) and try it.
--Z
"And Aholibamah bare Jeush, and Jaalam, and Korah: these were the borogoves..."