The Zaku suits were produced to work against the Earth-dwelling ESDF
It appears as aroughly 300' robot, with a single cycloptic search eye. The design is fairly reminiscent of WWII Germany's soldiers. The typical soldier's Zaku is green, high ranking officers, however, have been known to have blue or light red colorations (see Char Aznable).
The Zaku is known as the Stormtrooper of the Japanese and Otaku culture, that is, it is a highly recognizable figure depicting a massive evil force. That cannot aim its' weapons accurately.
Zaku units: "What?! No! A Gundam!"
*Zaku units are all destroyed, creating massive collateral damage*