Since somebody emailed it, just have them send it again.
The fact is, if it only contains a single file then once it's corrupt it is probably gone. Occasionally if there are many files w/in the zip you may be able to recover some of them with a free tool like mentioned.
But never pay money for a program that offers to recover lost files from a zip; if the best of the free programs won't work then it is extremely unlikely a paid program will do any good either.