At Dressrosa, when Law, Sanji and Luffy fought Doffy, only one didn’t face Doflamingo: Zoro. Why? Law and Sanji got defeated by Doflamingo, so Zoro facing him and taking a L would have been normal considering Luffy was Doflamingo’s main opponent. And the moment Zoro faced Doflamingo and was ready to attack him, Oda brought Fujitora a guy who hate Warlord more than anything to stop Zoro. It doesn’t make sense unless Oda made that on purpose because he didn’t want a Zoro vs Doflamingo.
The only reason for that is probably because Zoro was not a pushover for Doflamingo, he could have defeated Doflamingo but that would have meant the end of the arc. Where is the suspense? So Fujitora came and used his power against a non-intel Zoro, he send Zoro under the ground. Oda could have ended this fight as he did with King vs Sanji but no, he made Zoro to counter Fujitora’s gravity while Zoro was suffering by the gravity and pushed Fujitora few meters back. That was the first time to see a character besides the high/top tier to counter an Admiral, the strongest forces of Navy and also the moment Oda showed that Zoro is not a pushover for a top tier.
After that, Zoro faced Pica but again Pica was too weak for him, that’s why Oda gave to Pica a formidable Devil Fruit “Ishi Ishi no Mi”, the power to be one with any stone. Oda made Pica a walking mountain size golem. According to the One Piece site “the hand of Pica was the size of city in Dressrosa » so Golem Pica’s was the size of many cities.
So despite Pica being weak, Oda still wanked Zoro and gave him an island level feat. That was an amazing feat because only few people are capable to do that only with their raw strenght. In Zoro’s novel, people are already comparing his feat to a Yonko and a World’s Strongest Swordsman themselves.
So that means, Zoro’s feat is comparable to top tier feats. And again only Luffy is comparable because he defeated Doflamingo.
In Whole Cake Island, Zoro wasn’t there and Luffy beat Cracker and Katakuri. One thing people should understand is the fact that Luffy wasn’t weaker than Cracker or Katakuri, actually Luffy was YonkoCommander1 level since post time-skip. What made the fights interesting were the powers of those SC.
Cracker with his DF Bisu Bisu no Mi and Katakuri with his DF Mochi Mochi no Mi and especially his Future Sight. But again the Gear 4 was not useless against them because Luffy defeated them when he successfully touched them. So Gear 4’s strenght is more than enough for Yonko Commanders, it’s the versality and the external powers of the fighters that make them Yonko Commander lvl. So if Zoro was against them, Oda would have made Zoro win against them somehow like he did previously with Zoro’s fights such as Mr.1 or Monet.
Now let’s talk about Wano. Zoro was the first one to ever defeat another member of Worst Generation. Oda choose him and not even Luffy, he fought Hawkins and if the tiger didn’t came, he would have probably win because he cut one of the strongest card of Hawkins without taking any serious damages after that. He didn’t just defeat Killer and Apoo but he one shotted them and got the respect of Drake. Actually Zoro really shined against his fellows Worst Generation members.
And it’s not even the end, Oda gave to Zoro “Enma” the sword of Oden who wounded Kaido and decided to make Enma a cursed sword when Oda didn’t want to wank Ame which also cut Kaido, why is that? Because Oda wanted Zoro to have at least one sword from Oden and decided to make that, special.
And now when everyone claimed things such as Zoro is way weaker than Luffy, he is one of the 5 members of Worst Generation to face not one but two Yonkos. A man way weaker than his captain can really face someone who one shotted the latter? There is 0 logic in that.
So that means Zoro was already around Yonko Commander 1 lvl since the post time-skip. He didn’t beat Yonko Commanders but he faced 3 Supernovas, an Admiral and Oda gave him a special treatment such as beating the strongest swordsfishman, cutting a mountain size golem and defeating a logia without even touching her.
We can clearly understand that Oda didn’t make any mistake until now with Zoro’s strenght. Removing always Zoro when Straw Hat Pirates face someone strong because he has the potential to beat them or at least not being a pushover because it’s not possible with him. Oda could have made Zoro struggling and having extreme diff fights against any of his opponents or even loosing but no, Zoro didn’t face any loss this entire time because someone who trained everyday during two years with a top tier won’t be take out easily.
Now Zoro is facing Kaido and Big Mom two people from the elite again with his captain Luffy. So strenghtwise, Zoro was always next to Luffy that’s why Oda choose them to stand together front of Yonkous. They are the future Pirate King and World’s Strongest Swordsman, so it’s understandable for them to be front of two powerhouses.