two great rivals cannot coexist
Proverb meaning that two powerful or talented people cannot coexist in the same place or field; one will eventually dominate or drive the other out.
It's impossible for those two geniuses to be in the same department. As they say, two great rivals cannot coexist.
A Japanese proverb of uncertain origin, possibly derived from a Chinese saying. The literal meaning is 'two heroes cannot stand side by side.'