Rather than Zombie, is more what happens when you damage the core without actually shattering it or destroying it with a side dish of chunk ripped out of the body.
Yu's can have a more literal case of mental breakdown if the core is damage like that, it actually makes me wonder if when an actual mental breakdown on a yu happens it means the core self damaged itself out of the mental strain?
Then again I am talking about the more extreme mental breakdowns, not so much the short temporal ones that they can snap out of.