Zoro is Associated with Four Beings:
Tiger - Shark - Dragon - Demon/Asura
This is clear Hint that Zoro must become Strongest in Land, Sea, Air & Heaven !!
This is also a Hint about his Match-Ups
He Defeated Hyouzou (Sea) then Pica (Land) & now King (Air)
But ofc, these Three only represent Land, Sea & Air, they aren't actually Strongest in them
That's why Zoro will Claim the Head of the one Truly hailed as Strongest in Land, Sea & Air
ZKK Incoming
After that, it's finally time for Zoro's Goal to reach Heavens, that's why he will Defeat someone related to Heaven & Land of Gods
Someone who looks Noble & have Eyes like World Ruler who poses as God (Im-Sama)
That's Mihawk
This also Parallels Pre-TS where Zoro also had Five Major Fights
Hatchan (Sea), Mr. 1 (Land), Ohm (Sky)
And then he fought Kaku who was like Combination of all Three
(Multiple Swords like Hatchan, Iron Body like Mr. 1 & Endless Ranged Attacks like Ohm)
After that he fought Former Greatest Swordsman Ryuma (But Weak Version, that's because it's Pre-TS Zoro)