I have not found a single zip program on either Mac or Windows platforms that someone hasn't complained about. My immediate solution is simply to put additional links and files up here.
For Mac users, I recommend downloading the uncompressed files below. The program is just two files (plus the documentation).
Windows users have a LOT more modules to download, so you might want to download WinZip, the program I used for the Windows version (WinZip is currently the most popular zip program on Windows platforms), and use it to decompress the file you've already downloaded. You can obtain a copy of this from www.download.com. As a last resort, you can simply download the uncompressed files.
For the desired platform, click on each of these links in turn, and just make sure that they ALL go into the same folder.
UNCOMPRESSED DOCUMENTATION (PDF) FILES