The one thing is that I don't think Zoro vs king is necessarily confirmed. I mean, if Luffy isn't going to be on kaido's level post-wano, I don't see why Zoro should be on king's.
I think Zoro vs jack is possible, with Law taking on king. However, Jack doesn't seem to be the best swordsman, judging from what he did against asura doji. But still, the straw hats have a grudge against jack for Zou and Luffy said he would kick jack's ass. Since Zoro is Luffy's right hand, Zoro beating jack would kinda fulfill luffy's statement.
also, jack has more buildup than the rest of the calamities. He was first mentioned back in punk hazard and he was the villain of his own arc. I feel like this is because Jack will be defeated by Zoro while the other calamities will be beaten by other supernova.
lastly, Zoro still is foreshadowed to take on kaido, so Zoro can't be so fucked up from his fight against the calamities, that he isn't able to participate against kaido. Also, I think that jack is a lot closer to king than a lot of people think and that it isn't beneath Zoro to fight a YC3, especially since :
- Zoro has never beaten someone on that tier before
- someone of a similar caliber was shown to be significantly stronger than Luffy back in WCI
- Zoro will 100% go on to have other fights later in the arc.
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I also think Law is probably a better matchup for King than Zoro. Due to Law's room, he can easily counter King's speed and mobility in ways that Zoro simply can't.
Also, Law has one of the best devil fruits in the series, so it wouldn't be out of the question for him to beat a YC1. And while he was bested by doflamingo, that was 1 arc ago so he could have gotten stronger, and doffy knew all the abilities of the ope ope no mi, whereas king doesn't.