I'm 50% sure that thread just got "higher", but here's my thing right.
Apoo's current ratings are this.
Attack Potency: Likely
Mountain level+ (His "Fighting Music" put a deep cut into
Zoro and momentarily incapacitated Base
Luffy during the Siege of Onigashima)
Durability: Unknown, likely
Mountain level+ via power-scaling
Lets say the Mountain Level+ works.
Regardless of the amount of swords Zoro has, Apoo got one shot with 1 sword of Zoro's.
This is a bunch of Mountain+, so regardless, Zoro w/ one sword would massively upscale from him, putting Zoro in the gigaton ranges (or
Large Mountain level).