My proof is that Luffy and Sanji fought against something to increase their strength and learn Haki, Rayleigh said that in battle Haki flourishes more in battle and using common sense, if you don't put in practice the theory, you are learning a shit. And Zoro has a tons of rivals there too for that (why the fuck did you think author gave them opponents for all the three?), but he did not use it because reasons! Oh, he is special! Zoro here is the god and he does not need to practice like all the others!
It's not like we learned from his past that he is a hard worker concerning to train and his train consisted too with, guess it, yes, fightning opponents! What's the point of training your muscles if you don't polish them in battle?
He is the messiah, he learned Haki through cutting air! Ohh, what a talent! No, wait, he didn't need to do that. He practiced it mentally, like in that filler from DB where Krilin and Gohan trained in their minds. Bah, Zoro is the greatest. Let me lick your boots!
It's not like we learned from his past that he is a hard worker concerning to train and his train consisted too with, guess it, yes, fightning opponents! What's the point of training your muscles if you don't polish them in battle?
He is the messiah, he learned Haki through cutting air! Ohh, what a talent! No, wait, he didn't need to do that. He practiced it mentally, like in that filler from DB where Krilin and Gohan trained in their minds. Bah, Zoro is the greatest. Let me lick your boots!
Oh wait. Gtfoh with your utter shit that you have no proof.