“Two hands clap and there is a sound. What is the sound of one hand?”
When one realizes that reality is beyond duality, then the two hands are one. That is the sound of one hand.
“If you meet the Buddha, kill him.”
The idea here is that holding onto belief in the efficacy of the Buddha is grasping and therefore delusion. We have to destroy the notion that the Buddha is separate from us in order to realize that the Buddha is already in each of us.