The solution in theory is to force leap over to toth (if you're a guardian/jugg, if not use whatever the equivalent is) get the purple, then use force push to reset the force leap cooldown and leap back over to zorn.
Eh, what? The "theory" is that Zorn's tank ambles over to Toth, waits for the circle to turn purple, then heads back to where he was, same as everyone else.
This has never caused any issues when it's happened to us. I'd have to ask the tank if he was burning an AoE taunt on Zorn after the phase was over, but either way, it's been fine.