Zen is not a theology, it is a religion -- and religion without a theology is a unique phenomenon. All other religions exist around the concept of God. They have theologies. They are God-centric not man-centric; man is not the end, God is the end. But not so for Zen. For Zen, man is the goal, man is the end unto himself God is not something above humanity, God is something hidden within humanity. Man is carrying God in himself as a potentiality.
So there is no concept of God in Zen. If you want you can say that it is not even a religion -- because how can there be a religion without the concept of God? Certainly those who have been brought up as Christians, Mohammedans, Hindus, Jews, cannot conceive of what sort of religion Zen is. If there is no God then it becomes atheism. It is not. It is theism to the very core -- but without a God.
This is the first fundamental to be understood. Let it sink deep within you, then things will become clear.
Zen says that God is not extrinsic to religion, it is intrinsic. It is not there, it is here. In fact there is no 'there' for Zen, all is here. And God is not then, God is now -- and there is no other time. There is no other space, no other time. This moment is all. In this moment the whole existence converges, in this moment all is available. If you cannot see it that does not mean that it is not available -- it simply means you don't have the vision to see it. God has not to be searched for, you have only to open your eyes. God is already the case.
Prayer is irrelevant in Zen -- to whom to pray? There is no God sitting there somewhere in the heavens and controlling life, existence. There is no controller. Life is moving in a harmony on its own accord. There is nobody outside it giving it commandments. When there is an outside authority it creates a kind of slavery... a Christian becomes a slave, the same happens to a Mohammedan. When God is there commanding, you can be at the most a servant or a slave. You lose all dignity.
Not so with Zen. Zen gives you tremendous dignity. There is no authority anywhere. Freedom is utter and ultimate.