Principality of Zeon was founded by the Zabi family with the goal to gain independence from the Earth Federation. One big mistake made by the Zeon army was to drop a colony onto earth causing massive destruction. As a result, The Zabi family had been blamed for the cruelty and brutality.
Zeon army had explored into mobile suit technologies and invented Zaku 1. This technology that given them the upper hand in the first half of the one year. The Zaku1 was then upgraded to Zaku 2, like the ones you are in the pics. Some elite pilots of Zeon had customized their Zakus making them more personalized. These Zakus also bear their trademark logo or emblem.
Some of the top Zeon pilots are Char Azanable (Red Comet), Shin Matsunaga (White Wolf) & Johnny Ridden (Crimson Lightning). The red Gundam was stolen by Zeon and piloted by Char.