Z Plus
The MSZ-006 Ζ Plus (Zeta Plus) mobile suit series is a series of mobile suits developed by the Earth Federation and Anaheim Electronics. All of the Ζ Plus designs are by Katoki Hajime and Masahiki Asano based on the MSZ-006 Ζeta Gundam. However, the Ζeta Gundam was also a painfully complicated and expensive mobile suit and the Earth Federation did not want to mass-produce it as it was.
After the Gryps Conflict ended the Earth Federation wanted the design of the Ζeta Gundam to be reworked, so that it was more streamlined, less complex, and, most importantly, cheaper to manufacture, but so that it would still retain all of the major strengths of the original unit. The Ζ Plus line of mobile suits was the answer to the Federation's requests.
Read more about this topic: Z Gundam