How does they work exactly?
The Levels of TZ seems pretty "weird"

Mate used the Shards and the Level Range gets from 73 to 94.
Example
Frigid 81
Glacial Trail 83
Tombs 94
Catacombs 73
River 94
etc

How is the Level counted?
I used to think the Char level matters but doesnt seems like

When ur char leaves game for whatever reason, another char is selected to be the "owner" of the game, and newly terrorized zone is set from that characters perspective.

There is also a min hell tz lvl of 73 or something, so most likely a filler account became the owner of the game.

So the Owner has to stay all the time?

Or if original owner left, make all the chars you don't want to be owners leave and rejoin

If you want all the tz’s to be based on their level, essentially yes.