If ZKk happens, it’ll be after Luffy’s already beat Hyrbido in a 1 vs 1 but he gets back up again because of awakening.
With a scene like that.
Then it’ll be Dragon Kaido that Zoro kills, cause that’s what all the parallels with Ryuma are about.
We might even see three separate Kaido defeats. A round one defeat, where the Supernova all “beat“ him. Here Zoro’s big role will be opening the scar.
Then a recovery round 2, where he gets up and displays his powers of recovery with Awakening and knocks out everyone bar Luffy. Then you can get the Luffy vs Kaido one-vs-one where Luffy comes out on top, and Luffy shows himself to be the strongest fighter, the only one who can go toe to toe, solo, with Hybrido and win.
Then a final round, Zoan awakening kicks in
again and that’s where Zoro lands the final killing blow on dragon form Kaido.
I think that would satisfy the most people. Luffy proves himself the better all-round fighter, Zoro still plays a huge role in the defeat of Kaido and it’s not really an execution per se.