Like you said, the war is far from over. After Zoro take care of business underneath the dome he will return to take Kaido's head. Scabbards stayed the battle isn't over until Kaido is dead.
The question is can you see what's happening. Oda has been building up Zoro killing Kaido since Zoro defeated the Punk Hazard dragon. Remember, Luffy was there fighting the dragon too. We have Zoro's connection with Wano, Oden, enma, Scabbards and Ryuma. He even stated he wants to free Wano by cutting Kaido into pieces.
Unfortunately, it's ignored because some can't stand the idea of Zoro being equal to Luffy even though Oda told us they are equal during Thriller Bark when Kuma allow Zoro to exchange his head for Luffy's head.