I'm actually cool with Zoro reopening Kaido's scar then beating King. Queen seems like Sanji's arc opponent. I'm not so sure about Zoro killing Kaido though. I enjoy most of the Straw Hats so I see no issue with Zoro succeeding.
They didn't combine their attack in one like Luffy/Zoro with that cannon in Water 7 for example, each one slashed in a segment of the "X" did by Oden, so it's the same as attacking 4 differents spots.
So that won't make Zoro look better than a theoretical combination of the 4 of them.