Running your code on my local machine I encountered the following:
1. I got a prompt from WinZip requesting me to do something (click buttons)
2. I got an error if the zip directory didn't exist already.
I assume that WinZip on your server is also waiting for some user input (only you don't see the prompt...) - and then of course it's waiting and waiting and...
What's important: You need for command-line mode two add-ons from WinZip: WZZIP and WZUNZIP. They can be downloaded for free.
In your code you must then call WZZIP instead of WinZip - but that's all explained in the paper under the link I've sent you.