Just think about the scenario if Orochi is still alive.
Somehow the Sandai Kitetsu gets broken. Zoro in a pinch is in need of a third Sword, and is given the Ame-No-Hibaraki. Orochi, in a life or death situation (Kaido cutting his head off) awakens, and turns into a giant 8 headed Serpent towering over all of Wano. Zoro uses two Swords created by a Shimotsuki, and a Sword created by Hitestsu, to cut off all 8 heads at once.
At the end of Wano, Zoro gives Hiyori back Enma, and Momo back Ame-No-Hibikari, and having proved himself to the people of Wano he is given back Shusui, and Hitetsu gives him the Nidai Kitetsu.
Zoro will have avenged the death of Yasuie in the name of Shimotsuki (If he actually is one), and proven himself the mightiest Swordsman in Wano, by slaying the giant serpent.