Zoro was literally listening to Momonosuke announcement that Luffy was back and fighting Kaido.
He ordered them to go down and leave the fight to him.
Zoro hasn't mentioned fighting Kaido since 1010, he still has a link to Orochi because of Yasuie, someone needs to stop the CP0 it's not hard to do the maths.
1036 chapters and people still don't understand that nobody will outshine Luffy in a Arc, the idea that Zoro wins against his opponent and the goes to kill Luffy's one is completely ridiculous.