Teach is not a glass canon, he walked off a point-blank quake attack around his neck and a bisento strike. He can take Zoro’s attacks and keep going even if he gets scarred lol. Somebody way weaker like Lucci got scarred and wasn’t even knocked out by Zoro.
Kaido, who has high durability, recovery, and endurance, took an attack from a weakened Zoro prior to him mastering enma or obtaining ACoC. While BB, who doesn't have Kaido's durability, endurance, or recovery, took an attack from awakening Law using his awakening power and his 2nd strongest attack. Zoro's attack scarred she weakened Kaido, while Law's attack only gave BB a minor noise bleed.
Why is it whenever some people talk about Zoro's AP they always compare pre ACoC Zoro's AP, not post ACoC AP? There's a huge difference between the two.
After Zoro fought Kaido he faced a character who can withstand attacks better than Kaido l, even in flameless mode. That tells us what Zoro's KoH attacks would have done to Kaido.