yup, this is the main point a mac os9 newb need to know:
stuffit supports zip for OS9, but, depending on the content of the archive, it is not compatible with OSX zip and winzip/winrar´s zip.
so when you see a .zip file you never really know what it is and where to extract.
as a result you use .zip in OS9 only for stuff when it is clear how it was made and denote the format when sharing.
i like zip because it is faster, but its use should be kept to a mininum and reserved for big files. otherwise other people might open it in windows an break the content and render it unusable for OS9.
but even better, there is yet another third party zip app for OS9, which is also partially incompatible. if we would not have the chnace to ask the uploader, we could try zipit after something didnt work on OS9 and OSX board tools.
if you ever run into a .rar file which was made ith OS9, this "mac rar" format is generally incompatible with the "unix rar" for OSX and windows. "unix rar" can´t be opened in OS9, but there are "mac rar" apps for OSX.