I think Zheng He's treasure fleet must be regarded a bit like a fairy tale. I am sure the expedition happened but the size and type of ships were likely grossly exaggurated.

The problem with a lot of fantastical claims about China is that there is zero archeological evidence to back it up, while in Europe sources and usually paired up with archeological evidence. We know quite well the size of European ships at different ages because we have plenty of ship wrecks that have been studied. We have plenty of Galleys from Roman times e.g. that has been studied.

In contrast there are no large shipwrecks suggesting China built ships the size described in the Zheng He treasure fleet. So we have no account or physical record of ships of that kind of size either before or after it happened. That is highly suspicious. Large ships or constructs don't just spring into existence. Usually they evolve from smaller designs. You can just look at the Pyramids. We know of smaller ones which come before the larger ones.

When Europeans encounter the Chinese for the first time in the 1500s and later. The Chinese are remarking on numerous time on how large Western ships are. Western accounts also report on how small Chinese ships are in general. It seems very strange that a nation which had supposedly built giganting ships in the past suddenly became incaple of doing anything but building tiny ships. Even after the fall of Rome there was no such profound technological regression in Europe.

Also modern engineers cannot figure out how to build wooden ships of the size described by Zheng He story and they know far more about material science than people back then. Even in the 1900s with modern techniques Europeans could not build ships that size. Hence archeological, engineering and scientific knowledge suggests they were made up.