The metaphysics of Zen Buddhism is essentially Hinduism "stripped for transport" with a little bit of Taoist humor and Native-American Coyote energy thrown in for good measure. The Zen Master gives his students the opportunity to transcend the need for metaphysics.
Awakening 101
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An excellent online course on the mystical experience. It begins with the premise that Enlightenment is outside the scriptures. The broad range of links available on various descriptions of "Zen" experience is very useful.