my knowledge of eastern philosophies is liimted, having said that, ive read Toa te Ching, and am currently reading the analects of confucius and Chuang Tzu, so i may be better informed at some point. Everything i know about Zen comes from a western book called zen and the art of motorcycle maintainence, which i didnt finish because i didnt rate it that much. The book was essentially using motorcycle maintainence approaches as an analogy for what in the west would be called relativism. relativism is the opposite of absolutism. Most western regions and people (including my self, im a Christian) are absolutist, that is to say we believe in absolute truth. So either is a God or there isnt, either there is a tree in my garden or there isnt. My ability to know which is true might be limited but either one or the other exists. Relativists would say if you experience God he exists, if not he doesn't, if you see the tree it exists vice versa. Truth is simply what you experience. This view is found in the west, more progressive liberal christians, and some very liberal Muslims might take this view (im not this liberal). I dont know whether this is a Zenist view, i didnt finish the book (it was rather drawn out in making its point) but the book implied it was zenist.
Im drawn to taoist philosophy because i see the effects of Qi and am curious about it. Im reading Confucius just as a side line, but its interesting and i tend to agree with his ethics etc. Ive got a copy of the I Ching too, but i dont understand it, your post was useful counting.
as to the east west divide in religion: The three main western religions, Judaism, Christianity and Islam all come from the same root, namely Abraham and Yahweh. All three recognise the first few books of the Torah (Jewish text). Why these three have come to dominate the west not 100% sure. Probably a mixture of cultural aggression ( what i mean by this isnt that people of said religions are aggressive but that out reach to non believes is a core part of the message, the logic being when they die they dont go to heaven if they dont believe, so your doing them a favour), older patheon religions didnt to my knowledge have this to such an extent. Similarly im not sure if eastern religions have this focus. Secondly what they offer. Most people are afraid of death, a solution to this problem is attractive. This is a simplification and there are other issues, additionaly im trying to be neutral given my faith.
Western faiths are present in the East, both muslims and christians have been present in China's history at any rate, and of course Indonesia is a very Muslim country. Its true that eastern religions are rare in the west, ive met a fair few people with indian faiths that arnt migrants or of indian hertaige. I know from search Tai Chi website on the internet there are religious toaists in the UK, but i cant say how many.