Zen and Buddhism

I should like to talk about correlation between Buddhism and Zen. The last one is usually considered as a part of Buddhism, yet I think that they are very different.
Buddhism teaches impermanence. This implies existence of causality and existence of time. Buddhism builds its whole system on the basis of this concept: life will end, flowers fade, stones crumble... Hence we can understand the sympathies of materialists to this religion. Actually, their views coincide in many aspects. (Some say that the difference lies in the negation of morality by materialists, but this is very dubious point). Nearly in all. Like in materialism, according to Buddhism, there are also five or four elements which create associations and everything including our "self" -- atman is the product of that. Some, however, assert that Buddhism points at something that is beyond the existence of those elements, but that's not important now. The main point is that Buddhism acknowledges changes.
Now, what's the Zen view, as I understand it? Zen teaches that mind should not try to put the reality into its frame. The reality, according to Zen, is what appears to our sense, not more, not less. Reality is not memory and memory is not reality. Reality is the elusive present moment, the Now, whereof one can never say anything because everything we can talk about is our memory. And all our theories are built solely upon it. It seems obviously to me that such a view totally undermines nearly all Buddhist teachings concerning psychology and metaphysics. This also destroys the importance of any so-called mystical experiences because they belong to the past. In a word, Zen sets one free from all conceptions and from the past, it allows an individual to trust himself, lifts up the endless analysis of feelings according to a certain theory or dogma.