Hiya,
Don't know if this will help but:
When you've unzipped something it becomes whatever kind of file it is and the extension relates. E.g. if you unzipped a word document it would be a .doc
It is only whilst they are still zipped up they are .zip
You might want to go as if to unzip it again and take not of where it is being extracted to. Somewhere during the process there should be a path and the option to change it. Just take a look where it wants to put it then shut Winzip and go find the file you unzipped earlier....
Hope this makes sense!
Let me know if you need anything else,
Gaspode