Nansen said, "The mind is not the Buddha, knowledge is not the Way."
Case 34, Mumonkan, R.H. Blyth
The religions all have sacred texts, and sacred knowledge to be gleaned from them. What does Zen have? Nothing. What is a Zen Master the master of?
As Confucius remarked, "What you know, you know. What you don't know, you don't know." How close to the Way!