I thought Zeta basically refers to VZ, while Sigma Lite is exactly what the name implies.

 

Zeta is more of a proccess, rather than an individual platform.

 

Zeta is actually a set of components that can be put together in different ways to achive different products. Think if it like legos. Hard points like the firewall, front floor ban, rear floor ban, and a pillar are standardized. A lot of the stuff outside of the hard points can be changed with relative ease. That is what makes it flexible.