Many people doubt that Zoro would fight and let alone defeat King the Wildfire, because he might be even stronger than our mochi boy Katakuri.
I have to disagree. There are many reasons for my claim. First of all, One Piece is about 80% completed according to Oda. Since the difference between Zoro and Mihawk should still be huge, and with the story that much complete, Zoro soon has to start challenging very powerful swordsmen on the way to become the World’s Strongest Swordsman.
Secondly, there’s no way that Zoro wouldn’t want to fight King if he finds out that he is a swordsman and Kaido’s strongest henchman. Not to mention that Zoro almost always faces the right hand man of the opponent pirate crew.
Thirdly, like everyone pointed out, King’s name is King the Wildfire, and Zoro stated in Punk Hazard that he would learn to cut fire.
Those were the reasons I believe Zoro would fight King. Now let me explain why I believe Zoro could defeat him, even though King should be at Luffy/Katakuri tier.
Like I said before, the story is 80% complete, Zoro has to start defeating monstrous swordsmen. Zoro promised Mihawk that he would never lose (to a swordsman) again. He has no choice but to win, especially since promises in shonen are a huge thing.
Now coming to the power level part, I do believe that Zoro is weaker than Luffy, but not by much. Zoro and Luffy will have a minor difference in strength like Rayleigh/Roger. Their difference wouldn’t be huge like Yonko/Yonko Commanders. If Luffy is much stronger than a top Yonko Commander by the end of Wano, then also Zoro needs to be slightly stronger than a top Yonko Commander.
Zoro also has been a monster in the New World . He has barely been trying and yet destroying characters like Pica (who was Vergo level).
His power is unknown at this point, and it’s baseless to say that he can’t beat a Yonko Commander.
I’d try to explain why Zoro could still be near Luffy:
1-He could grow just like Luffy did in Whole Cake Island. There won’t be any shortages of enemy in Wano. With the war between Kaido, Big Mom, Navy, and possibly other forces, Zoro could fight very strong characters to grow to a whole new level. Luffy will still be stronger but Zoro will reduce the gap since Luffy is in prison while Zoro would be defeating enemies.
2-Zoro trained hard with Mihawk for 2 whole years, while Luffy trained with Rayleigh for 1.5 (Rayleigh returned to Sabaody Archipelago half a year before Luffy). This may have led to Zoro having a more rewarding time-skip. Luffy may have grown much stronger in the New World but Zoro could have gotten stronger at a faster rate than Luffy during the time-skip, thus making the difference not so big.
*Theory by HellUnleasher