@Tikibo
Certainly. I would never argue people are born with or without certain advantages. People are all different there's no doubt about that. However, Zenitsu is only arguing that Himejima can only do it because of his size, and predisposition. However, while they said Himejima is the strongest Pillar, it's safe to assume that it's an ability that all the Pillar's possess or have trained to some extent or another. Zenitsu even argues that it's impossible
before seeing him do it. It becomes more evident when Genya comes into the picture and talks about how there is a technique involved in order to accomplish it.
In addition, your statement also doesn't take into account all the crazy nutty crap they've literally seen people do before this. Once again, I'm going to reiterate that his comments make sense in
our world -- which I've
already said , I'm talking about his comments/personality in the context of
their world. Given what we've seen not only here but previously as well, then you can make further slight analysis on his character. That's not to say everyone is capable of succeeding in this sort of training by any stretch, but at the very least, the laws of physics and common sense don't necessarily apply in their world. There's still the considerable wall of talent that will stop a vast majority in their world. But even in this chapter it's noted that Tanjiro's little trio are considered "monster" talents themselves. Like I said, I think Zenitsu is a super-talented dude who is just lazy, slightly-cowardly and in addition perhaps doesn't have enough faith in his own ability. As I said these are just my opinions on it. It's not like what I think really matters in the end anyway. ?
As a side-note which is slightly related but not really, your post reminded me of an old quote that I love: "Not all who put effort in will succeed. But all who succeed had to put in effort."