So by the time the timeskip started, Zoro had already beaten a 3 billion pirate, who can rival a Yonko?
You think Zoro would achieve his goal on a straight course?
We don't know what his frozen bounty was. Could well have been 160M.
He also didn't rival any Yonko in the present storyline. That was the past. Present Mihawk couldn't scratch Jozu and was gardening with Perona and baboons.
Zoro vs Mihawk was cool when Baratie Arc came out and we were little kids.
Nowadays, let's be honest it can only come out as a disappointment. People anticipate the omegalul monstrosity of a fight, but Zoro is not Luffy and Luffy has set the bar quite high. You think anyone besides Luffy gets a fight longer than five chapters?
Back then the distribution was a bit different, stakes were also much lower, plot less dense. East Blue Arc is mostly a better written Dragon Ball with Pirates and ethics. It's here were Zoro vs Mihawk belongs, really.
Current story...Honestly three chapters of Pre-skip Zoro beating Mihawk in a flashback while he slices Shiryu in half sounds more satisfying then 3 chapters of current Zoro beating Mihawk in present time.
Honestly there's not even character development for Zoro left, he already can do anything now. People want a bossfight equivalent to a vs Katakuri or vs Kaido, but what is even going to happen in there? Zoro's fights are always the same:
Zoro: "I can't cut you!"
Enemy: "That's right you can't cut me!"
Zoro: "Lol just kidding"
*slash*
The entire WSS thing is stupid, as hinted in the story, where it never made much sense and now where we are at the point that entire countries get blasted to smitherens by deranged world kings...
If there's any positive message behind Zoro vs Mihawk (East Blue), then that fighting just for the lulz is retarded. Zoro already moved past that when he asked Mihawk to train him, so he could be stronger for Luffy. And they say that Love is like a Hurricane, can't see Mihawk dealing with that.
You know whats the opposite of King of Hell? King of Heaven! Zoro is totally on a new goal, you know he just wants to be by his side...