
This panel is interesting. Both Zoro and Luffy use observations haki to tell another attack is coming
I say this is observation haki because Apoo hasn't started charging up yet. Apoo starts charging the next attack in the NEXT page.
So both Zoro and Luffy are HYPER aware in this panel. Zoro is even blocking some fodder guy behind him while focused on Apoo. YET LUFFY STILL GETS TAGGED and Zoro gets surprised.
I think this mean Apoo's attacks are unblockable. Like they can be perceived to some extent since Apoo needs to charge but when the attack happens, you cannot block it. You just have to be out of range as Apoo stated in order to not get hit.
The only other theory is you should be hypersonic to maybe dodge the attacks IF THE ATTACK IS UNIDIRECTIONAL AND SPEED OF SOUND. By this I mean Sound moves in all directions at the same time so maybe Apoo's attack also does. If that's the case then once again it can't be dodged and you have to be out of range just.