OK, you need two things:

1. A software which runs on Mac and can make zips or .rar files
2. Somewhere to upload the file

OK so you say you made the zip - what program did you use? Stuff-It? Is it one which will allow Windows users to open it okay?

For file hosting - I would suggest you check out sharecg.com - they offer free hosting and if your item gets enough downloads they even pay you a small amount (based on share of advertising revenue).

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"you are terrifying
and strange and beautiful
something not everyone knows how to love." - Warsan Shire