Giant ZRK was the first battery-operated Zoid introduced in the American market, hitting store shelves in 1983. Building upon the success of earlier wind-up Zoids, Giant ZRK was produced until 1985, by which time it had been joined by newer variants on its chassis, including Mammoth and Gordos.
Known weak points of Giant ZRK include a delicate and breakable part of the neck movement mechanism. In addition, the leg mounts can occasionally get out-of-sync, leading to unstable walking. See this photo and diagram by bughunter426:
Scans of the original instruction booklet for the 1983 Giant ZRK released for the American market: