Quoting the opening caption from
Zoids Chaotic Century exactly:
"In the far reaches of the
Milky Way, on the
Planet Zi, there exist metallic
life forms that posses superior fighting skills. These are the
Zoids.
Warriors by nature, Zoids have been used as the ultimate
weapons in an ongoing war between the
Imperial forces, and the
Republicans of Planet Zi."
Essentially a Zoid is a large,
sentient,
mechanized being that is extremely loyal to its pilot.
For the full text of all Zoids prologues, see:
http://www.zoidsunofficial.coolfreepages.com/Prolog.htm
This writeup is under the GNU Free Documentation License