Yes, Zoro solos Kaidou.
He proclaimed 'I' came not 'we' to slay Kaido.
He one shot Appo and Kaido one shot Lufffy.
He inherited 'loved by all, respected by all' Oden will.
Very important point is only Zoro is a 'samurai' from the protagonist side and we know this arc is heavily centered around samurais.
Other SN including Luffy has nothing to do Kaido for two reasons. They are pirates and they are not having traditional Japanese swordsman.
It is Zoro vs Kaido
Luffy (if he doesn't run away like he did in WCI/Udin)+Kidd+Law+Marco vs BigMom