Zeus was more than wary of the Primordials. In the first place, Zeus had always been on the edge with his brothers- Hades and Poseidon. However, after he began siphoning energy from Chaos, he was now stronger than those two, to the point where Zeus would be left with at least 30% health after beating either one.
However, that wasn't the case with the Primordials. These beings were literally what made-up reality. It wasn't that they were the 'God of' or 'Goddess of' anything, they were literally the 'anything'
Such powerful creatures would treat Zeus as a child, and each and every one of them could comfortably beat him. It could honestly even be considered bullying. However, things were different now. None of the Primordials retained their original power, after all, they've all woken up from a slumber of many eons.
