In
Mobile Suit Gundam, the
Zeon forces employed Zaku's as their front line mobile suits. Interestingly enough, I understand that sales of the green Zaku (and the cooler Dom units) outperformed the more brightly colored Gundam model.
According to the Gundam Models Manual, Vol 2 published by MediaWorks, there are two major variants for the Zaku, the MS-05 Zaku I, and the MS-06 Zaku II. The Zaku II is the version featured in the Mobile Suit Gundam movies and television show, and the Gundam Side Story Dreamcast game.
For more information in English, please consult www.gundamproject.com. While the official English Bandai sites are nice, those sites tend to lack the more in depth coverage which fans find useful.