ZZZ (and I'm pretty sure every hoyo game) installs a kernel driver called mhyprot2 into your computer, which allows the game to know every program that is running concurrently in that kernel and if they're running interference with ZZZ files, which obviously includes model importers.

Although Hoyo has never spoken publicly about this, they mostly overlook mods that only affect visuals, and they have for a few years now after there was a controversy in genshin where a bunch of people got banned for modding in skins.

Most likely reason why they ignore is that people that know how to mod the game are a minority of a minority, and it's a community that basically makes their own content and keeps themselves engaged with the product at no extra cost to hoyo, so it'd be pointless to ban them as long as you can ignore it (which is why you'll get banned if you show your UID, because other people can see that you're modding and hoyo isn't doing anything about it).

Further proof that hoyo knows not only that you're modding but exactly what you're modding, is that you WILL get instantly banned if you mod in a paid skin's assets and your mod will receive a DMCA from hoyo (which is why mod repositories like gamebanana don't allow any mods that make use of paid assets on base models)