Went about 25-30 tries WITHOUT the zeta on Bossk's lead, but I got it first try after the zeta.
Remember folks, Dengar is just there to keep Chewie from stealth, and doesn't really do much after that.
-Make Bossk your fastest character, followed immediately by Boba. Cad/Greedo/IG-88 don't really matter, just make them fast but with Crit Dmg triangles, and offense crosses (if possible).
-Mod Dengar for flat health and protection. He just needs to survive Pulverize from Chewie.
Pretty simple. You want to hope that Han hits Boba and they focus him down (thereby removing Stun for his first turn) or that Han hits anyone except Dengar and Bossk. Dengar HAS to survive. If they Stun Bossk, you'll probably have to restart. If they stun Boba but don't kill him, you'll probably have to restart.
Dengar MUST get critically hit by Chewie and get put into stealth. If he doesn't you'll have to restart.
Should only take a couple tries to get this RNG setup. After that, you want to use Bossk's taunt. Boba uses Execute on Chewie which should leave him without much protection (if any), followed immediately by Bossk's Hunting Party. Chewie should be dead (or near dead). Do NOT use IG-88's AoE. Instead use his basic. IG-88, Greedo, Cad, etc. (whoever is next) should be able to finish Chewie easily.
Next, focus Han and then Lando. With Bossk's taunt up and no Chewie, you really shouldn't have any issues from here.
NOTE: If you can't kill Chewie with Execute and Hunting Party, your mods suck or aren't set up right. I was able to take Chewie down with the above teams pretty easily. Cad makes this event even easier, as he can Stun Han and/or Lando to make their damage trivial.