Zeers or Chexmix in P3?

The reason of the Chexmix is the ability to multi hit with zHan. For this reason, he's a far better character on himself all the mechanics of both raid and lead. From the lead, your Han reach 85% counterchance with the ability to hit 2 times in a row for the first counter. With the deathmark, it's not much about the damage you get from this debuff but it's for the effect of the "taunt" it triggers. From that point, with the Standalone and the offense up you'll gain something close to 15 000 offense or more depending on your optimisation.

With a zVeers, you get a multi assist attack and then what ? Nothing and you won't gain tenacity from anyone so that you'll get daze and stagger or debuffed.
zVeers is far better in p2 with a full trooper squad (no DT).