The Zetas are one of few races in a worse situation than humanity. By example we can still reproduce naturally. They cannot: they just clone themselves. I have great sympathy for their kind & I can understand the beliefs that sponsor their actions: unfortunately for all of us they broke the Rulz: (no typo) Let each soul go their own course. In doing so they took advantage of the human thirst for power & many years ago nearly doomed us all to their own fate. Research Dows, Dals, Zeta 1 & 2, Alex Collier & the book Gods of Eden by William Bramley.
They're not necessarily evil, they have a balance of gifts & turmoil just as we do. It's my view that they're just trying to save their kind. However there are many species of Zetas & while most of them are benevolent, some are not. They are also, like most of who's out there, both physical & non-physical beings;- extremely spiritual.