Throwing a completely new thought into this: what if the Florian Triangle is the living place of a Zou herd?
I mean, the Zou we know has a strong fog around itself, most likely created by Zou itself and it is said that strong sea currents are around it, which makes sense considering that Zou has to walk to move forward and that legs of this size will certainly create currents while moving forward.
A strong fog is something the Florian Triangle has as well and despite it not being shown or mentioned in the Manga, would it make sense that there are strong sea currents, as they would also lead to ships going of course and eventually being missed.
Furthermore would the size of the beings from the Florian Triangle fit. I mean, so far have we only seen two creates that would be big enough to dwarf Thriller Bark - the worlds biggest ship - like this. One being the Mountain Whales, like Laboon, and second would be the elephant Zou.
Now is it quite unlikely that Mountain Whals would lurk around above the surface of the sea like this, while the Zou-Elephants are more or less forced to do this.
Zou has to come from somewhere and as I think that it is a natural being would it not be weird if there were actually other Zou-Elephants around.
Though this would create two questions:
1. Why is one Zou seperated from it's herd like this, lonely travelling the New World while the others are in Paradise?
2. Why has nobody ever seen the Zou-Elephants in Paradise to report about them?
The first could be explained quite easy, if you're willing to believe it.
Zou might have been seperated from it's herd somewhen and is since then trying to find it again. This wouldn't be unlikely considering that at least real life elephants are animals that strongly value their herd/family. Though this would then again create the questions as to how it could even get seperated from its herd?
One answer might be the war form 900 years ago. It might have unleashed powers that were strong enough to drive one individual away from it's herd or it was somehow used in the war and brought to the New World? I don't really wanna go further into this as the ideas are already far fetched, but I think you also get the idea behind it.
On the other hand might Zou have left the herd voluntarily, going to something like a Zou-Elephant graveward, though why hasn't it reached that place yet? I mean wandering around for so long and being this big, Zou should be able to reach that place rather fast, shouldn't it?
The second thing could also be answered rather easily.
If one of the Zou-Elephants can arleady create noteworthy sea currents and a dense fog, then what can many of them do? The sea currents and the fog might simply not allow anyone to actually reach the Zou-Elephants in Paradise as they are too strong for the ships that can be build right now to reach the elephants.
Just a random thought of mine,