Quick example of skill stacking: You won't be the world's best chess player or boxer, but, hey, being the world champion in chess boxing (https://en.wikipedia.org/wiki/Chess_boxing)? That may well be within you reach.
This is gimmicky. Everyone knows they can be the best in the world at some random and obscure task nobody cares about. This sort of thing is a complete waste of your time. Better to focus on improving at one or the other.