I wonder if Zio's armor might have been part of the source of his power? It's very unique.
Zio's armor is cool!
But seems very similar to what Juza and his "clones" wear - and they can only perform non-magical techniques like zan, wat, foi (which regular palmans can do - yes, I think Juza is a fake magician). Their armor could "shift" some power (since lashiec’s armor have done that), but my bet (to perform real magic) goes to Zio's arm.
No one on Motavia had that kind of power in Zio's time. The government had completely fallen to pieces. Zio didn't possess real power at first, but he definitely seemed to gain it as his reputation spread.
I was trying to suggest that zio hadn’t political influences but had to have something else… 'magical' potentialities?.