Not really the right forum to ask, but there's a format option for zip codes in the special category. Otherwise, you can use the personalized format and enter five zeros (00000).
Luis C.
General Disclaimer:
Are you seriously taking the advice and code from someone from the internet without testing it? Do you at least understand it? Or can it easily kill your server?
How to post data/code on a forum to get the best help: Option 1 / Option 2