Zoro's power by the end of One Piece will be comparable to that of a Yonko.
If Zoro from One Piece was transported to the world of Demon Slayer, what would his power level be? - Quora
Shusui, One Piece Wiki
How Zoro's Heartbreaking Loss in One Piece Changed Him Forever
One Piece: Why Mihawk has Advanced Conqueror's Haki, explained
One Piece: Zoro's Sword Upgrades In The Final Saga, Explained
One Piece: Zoro's Final Opponent May Not Be Mihawk
Someone will explain to me why Zoro's promises>Luffy's promises and supposedly the battle with Mihawk is guaranteed, and Shanks will die from Teach before the battle with Luffy? : r/OnePiecePowerScaling
One Piece Film Red Movie: Ending Explained - IGN
4 One Piece Powerhouses Besides Mihawk Who Have Humiliated Roronoa Zoro in a Fight