Admiral level AP =/= the character is on admiral level.
Otherwise Enel would be admiral level.
But Enel does big attacks with Arc maxim. Very different from Zoro.
Every other Enel attack couldn't kill a single person, including fodder. Which is different from Zoro.
For example, Zoro avin Admiral level AP easily translates to Zoro has admiral level defence. Since haki is what translates to AP, haki is also what used to block.
By that I mean, Zoro should be able to block the Admiral level attack he himself used.
See how that works. This is a physical stat unlike Enel whose powers don't actually affect his physical stats. His admiral level AP using maxim doesn't give him admiral level defence or speed or whatever