What are we even talking about?
If the subject wasn't Zoro, this wouldn't even be a debate
Assuming that Zoro doesn't have greater authority than any other SHP member bar Luffy
Then
Why would Chopper ask Zoro after Luffy already denied him?
If Zoro doesn't have authority, why ask him?
And likewise
Why after Zoro denied too, why did Chopper stopped asking?
If Zoro doesn't have authority, why stop after he denied, and instead just ask someone else?
Pretty clear that Luffy > Zoro > others
In fact we see this
That is FULLY APPROVED BY ODA
Like it or not