beating Moriah was the main goal/opponent/fight of that arc
Moriah not Oars
Kata was Main fight/opponent of WCI,
Doffy DR
Lucci EL
Enel Sktpea
.....
Zoro didnt even take part in FI when luffy fought hody 1 vs 1 as finale
Zoro got to fight Hody mid arc... and he got captured by a weaker Hody than the one Luffy fought lol
Moriah was the main antagonist. he was not the main fight. the fight vs Moriah was rather anticlimatic as Moriah was almost down for the count already by receiving a remote pummeling from nightmare Luffy when he was sitting in Oars.
Kata became the main fight of the arc as Luffy was incapable of defeating the main antagonist.
Lucci was Luffys main fight. he was also not the main antagonist. that was Spandam and the WG with their buster call.
there is also the fact that Luffy/Lucci fights only purpose was to stall Lucci. Zoro returned the key. Franky and the rest saved Robin.
Sanji outwitted the buster call.
Enel... you are not even trying anymore.
Zoro one shot hody underwater while Luffy was left for dead after the fight. what a lucky break that Jinbe had the right blood type.
Luffy in the same situation as Zoro would have become a hammer and get captured without putting up a fight.
at first I was of the same opinion as you and thought that Zoro will never particpate in the main fight vs Kaido and or BM.
now, after he received Enma and the whole story arround Ryuma being canon I am not so sure anymore.
there are many implications on why it is very likely to happen.
for instance: this arc, Zoro was the one wandering off alone and stumbeling upon major players of wano like Yasuie and Hiyori.
Zoro was the one to befriend the princess of the arc this time, not Luffy.
Zoro was the one to befriend the oldtimer who has strong ties to the main plot of wano, not Luffy.
additionally, since Zoro is a "samurai" he is almost bound to play a huge role in wano.
compared to Sanji and his cake in a food themed arc Zoro is incapable of providing anything else than cutting down strong opponents in a samurai themed arc.