If it’s more power then by default it takes more stamina.
Swordsmen aren’t brawlers who fight specifically to way the opponent down. All Zoro needs is one good attack and the fight ends. So yeah, he isn’t using everything when he’s just blocking and parrying and stuff.
like Imagine those pages where Zoro is just clashing with a swordsman, like why would he have black armament hardening on just then?
And Oda isn’t lazy, every time Luffy is specifically in a serious situation, he makes her to draw the black armament to tell us Luffy is serious.
The interesting question about Zoro is why isn’t he using Black armament now vs Kaido? It’s not hard for like last chapter when Zoro used Onigiri, he could’ve just drawn the black stuff if he wanted.
I think the answer is that Enma will drain Zoro the moment he actually tries too hard with the Armament