Saw this a few days ago - and thought I'd take a stab at it.
If the universe came into being and contained a chaos of nitrogen and phosphorus and all other manner of elements, and for some reason several exceedingly simple amoeba came into being... formed out of incidental occurrences in the chaos, then some of them formed another amoeba by having the nature of replicating themselves, then some of those diverged into different types of amoeba and eventually (as the amoeba died and replicated) evolved into other things - one of which was a plant, and then a plant sprouted, and then eventually that became a tree, and the tree produced oranges... could the oranges be said to exist as separate entitites outside of the universe? If one of the oranges looked at another and said "You know, we were created in this world and we are apart from it" and all of the other oranges agreed - would it change the fact that they were part of the world itself? Aren't they a particular part of the universe just as everything else is? Not a separate being thrown into a world, but a part of the world - just as a lemon seed inside of a lemon is not a creation thrown into the world of fibers and juice that a lemon is composed of - but it is a part of the lemon itself, which is part of the world, and of the cosmos. It was formed from it.
Just as that lemon seed is part of the lemon and the tree that it grew from, we are part of the world, and of the universe. We're just more conscious and (arguably) complex than the lemon seed, but we are just as much a part of the cosmos as it is. We all came from it. As Alan Watts said (paraphrasing) "As an apple tree produces apples, the earth produces people. The apple tree apples, and the earth peoples."
[ame="http://www.youtube.com/watch?v=ppyF1iQ0-dM"]YouTube - Alan Watts "the Earth is People-ing" Animation[/ame]
When I hear about zen and other forms of belief, I dislike the terminology. It's esoteric and doesn't matter nearly as much as the concept it is describing. If I were to call the realization of reality "Brahman" or "Ishkabibble" it wouldn't matter - it's the concept that matters. Knowing a name is one thing, but knowing the concept that underlies that name is another. So many times, though, people are discounted for not being able to define the "atman" or "non-dualism" or "authenticity", but the terms are known. Christians scoff at other christians when one doesn't know the proper translation of a hebrew text. The text is meaningless, it's the matter that counts. I might as well ask a solely english speaking person "Donde es la luna?" at night and, when he shrugs because he doesn't understand me, laugh at him because I assume he doesn't know that the moon exists. Or laugh at a man when he shrugs after I ask him "Could you point at your pollical" and he fails to point at his thumb. Tao, zen, non-dual self, zazen, satsang, ego, acute coryza, etc etc. All the same. So often, though, we get attached to the name and not the understanding of the concept.
In the words of Alan Watts - "The sound of rain needs no name."
This, of course, leads onto things that uproot some of the societal beliefs that many of us take as simply granted and not needing a foundation...