I am listening to the P1's now via a fully balanced home desktop amp that has lots of power. That is the thing with the P1's they take more power than most portables offer - to sound good.
The ZAX are very easy to drive...quite the opposite.
The Tin P1's with their single crossover-less Planar driver is on a
very different level than the ZAX for detail retrieval. Cost quite a bit more too, so they better sound good
Saw today in the P1 thread that photos of the Tin P2 have been seen on several social media sites and that the release should happen soon-ish. If you were interested in the P1's...I would hold off and see what the P2's bring. Maybe they will be easier to drive? Have a Dynamic driver, too, for sub bass?