Try new 2.9.4 version at
I've tested it on fresh Lion install and it seems to associate
itself with .zip and other files just fine.
To simulate fresh install you may delete file ($USER is your username)
/Users/$USER/Library/Preferences/com.zipeg/zipeg.properties
aka
~/Library/Preferences/com.zipeg/zipeg.properties
reachable from Finder via
Finder: Command+Shift+G
~/Library/Preferences/com.zipeg/