4 encounter: Low diffed
His four encounter was with Fujitora and he managed to push him black and overpower his Gravity.
Zoro has shown that he can also tank small attack from top tier with how he managed to remain concious after being attacked by Fujitora and even managed to respond.
Still Fujitora was a good deal above him but the author showed us that Zoro was no longer getting humiliated like pre Time Sky Once Low diff.
5 encounter: Mid diffed
His five encounter was with two top tiers Big Mom and Kaido.
In the fight he has gone from failling to damage the enperor to make one Scream to the other to dodge and finaly he has gone from doing superficial damage to a top tier to doing serious and perma damage to thé most durable of them Kaido.
Not to forget He has shown the ability to countered most of their attack and tank theie Low tier move to tanking an equivalent of a Yonko ultimate finisher in Hakkai and even hold it back for some moment without his Sword breaking.
This Zoro showed by that AP wise and defensive wise he Can push a top tier to mid diff before going down cause they will need to use one of their strongest attack to take him down when Hakkai couldnt instantly.
I disagree here - Fujitora didnt low diff Zoro.
They clashed and Zoro ended up looking better.
Because unlike Fujitora who pushed Zoro down due to surprise power without obstacles, Zoro pushed Fujitora back through obstacles.
The fight moved on to another clash between Zoro and Fujitora which was portrayed equally and that's it. Nobody low diffed nobody.
Kaido and BM never mid diffed Zoro. In fact, neither of them have managed to accomplish anything versus Zoro on their own.
Nobody was targetting her because she is simply an inferior Kaido and Zoro bested Kaido in all 3 of their encounters.
He ultimately failed but that was because 2 Emperors combined their power to severely damage him. On their own they arent capable of it.