Reading this scene the first time, I was like 'damn Luffy, gone so quick, you not gonna check on your boy Zoro like the others'.
But then I think this panel sums it up nicely:
I really think Luffy wholeheartedly believes, that Zoro can take anything. It's like how a kid would hold highly their idol hero. The way Oda depicts Luffy confidence in Zoro, is different than how he's confident in other members of his crew.
It's like Luffy think Zoro is either completely on his level of power--ambition--resilience, or even more so tbh, so that's why he doesn't stay for the "Zoro are you going to be alright?" and doesn't even looked too phased, he just moves right on to continue fight Kaido and even trolling him.
Kinda reminds me of something Luffy said I think during Baroque Works, something like "how can this happen, when you were here Zoro?!" or something like that.