Actually there is a lot of “something” at the center of a black hole. Like several times our sun’s mass worth of something. It just doesn’t take up very much, if any, space. Wrap your mind around that.
Nothing just isn’t anything. Take all the stuff in the universe and get rid of it. That’s nothing. It is “unstable” because if you put a lot of something next to nothing, it tends to want to fill up the nothing.
Take a jar and suck all the air out of it with a vacuum pump. Other than a few random molecules, you have a jar of nothing.
Like Indistinguishable, I don’t see what the big deal is about zero or nothing when there are so many other phenomenon that are much more difficult to wrap your mind around.