Instead of using Winzip, which costs money, I use 7-zip, which is free and better. 7-Zip can create and open zip files but its own 7z file format gets better compression and is faster as well. Plus during encryption it uses AES256, which is safe enough for the United States Defense Agencies.
Over at Computer Forensics World, someone is trying to break a 7-Zip file because he suspects that there might be child pornography inside. Unfortunately for him but fortunately for the reliability of 7-zip encryption, he doesn't seem too successful.