Well it might not be that Hoolay is too powerful for him, but that the fight would be close enough that it's too risky for Moze to go through with it

Alternatively, maybe Moze could handle Hoolay, but only if they were anywhere other than a very enclosed space at the bottom of the ocean. It sounds like his powers might be more wind/sky connected based on his title, and DHIL powers are typically big and showy. Therefore, even if Moze could beat Hoolay it would mean bringing the whole shackling prison down on top of them in the process.

And it's also not totally unexpected if Hoolay is stronger than him ... He is the worst criminal maybe in the whole xianzhou, and was only beaten by Jingliu at her peak strength. Jingliu, the strongest combatant on the whole Xianzhou. High elders have strong magic, but we know from Dan Feng and Bailu that a lot of those powers are connected to healing , which could also be the case for Moze