Dude. You should know why Akashi shits just from reading the Manga/Watching the anime.
-Zone Kagami and Zone Aomine were playing on par with each other more or less.
-Akashi w/ Emperor Eye was beating Zone Kagami with ease until he reached the bottom of the "ocean of the Zone". But since Aomine can reach the bottom too, he'd have the advantage just like Kagami did due to his wide sphere of defense that Akashi can't act in.
-But then Akashi uses the Zone and shitstomps Aomine just like he shitstomped Kagami in the last match. Akashi was still breaking Kagami's ankles left and right, and ran circles around him when he used the Zone. Kagami canonically couldn't keep up. That's why he needed the second Zone. So why would Aomine be able to do so much better that he'd win?
5 v 5? Rakuzan shits simply because:
1. Zone Akashi would solo the whole team. If the ace gets stomped, the rest of the team doesn't stand a chance. That has been shown many times.
2. The 2nd Zone was needed to counter Zone Akashi. Aomine can't open that door.
3. Zone Aomine would get raped. Again.
To-o gets the Seirin treatment, except they don't win. They get murderstomped.