User blog comment:Shadow Archon/Hypothesis: Explaining away the Zerus Discrepancy/@comment-4817-20150513233805/@comment-26354460-20150514000341

-Mengsk's communication device was found at Char, but if you do the Zerus missions after Kaldir and Char, the Brood that picked up the devices delivers them to Kerrigan at Zerus. [] The conversation here takes place in real time with Mengsk at Korhal and Kerrigan at Zerus.

The issue is why don't the Protoss have better communication tech than the Terrans if they have much better technology?

-Zerusian Stingers are specifically stated to be floral Zerg meaning Zerg plant-life does exist, and the Quillgore are also stated to be Primal Zerg. Spore Rays also feed on Zerg Micro-organisms, and I can't possibly see that happening if it isn't part Zerg itself. Are there any other critters beyond those?

From my poking around in the editor, nothing on Zerus is outright stated to be not Zerg, and practically all the life-forms that can be interacted with are stated to be Zerg. There's no outright statement about the issue, but I feel the implication is heavily leaning towards all life being Zerg in some form now.

I can't really argue that point further or prove it conclusively given the lack of evidence, but that's my opinion given what we do know.