Please review this link and if you still need assistance please let us know. Either way please let us know if you got it working or if you need further assistance.

You need to have WinZip 9.0 with the Command-Line Add-on in order to have good success with this, otherwise I'd recommend another method, perhaps .CAB as Lonkero suggests in this other thread.
 
I would also probably use SELECT CASE myself instead of so many If statements. Either one will work though. 

WinZip Command Line Support - Download
http://www.winzip.com/downcl.htm

 
Please review this thread.
 
Recursive Zip