Hi Adam
Just a quick "I disagree" from my corner regarding some of the things you have written. Obviously we can never truly argue with what we "believe", so please don't understand what I am writing the wrong way. I am not trying to say "I am right", rather I would just like to highlight a different perspective.
You wrote:
"I believe that you can use Zen regardless of being Christian, Muslim, etc. ... The great thing about Buddhism is that you can use what makes sense to you.
(...)
Sila (Buddhist ethics), Samadhi, (concentration) and Prajna (wisdom) all have to come together for Zazen to really unfold. No right view without deeply realising the four noble truths either.
I don't doubt that sitting down and entering deep meditative states can lead to great realisations...it just ain't Zazen IMHO.
Buddhism split into dozens of different school precisely because "using what makes sense to you" did not make sense in a communal setting. Once differences in practice and/or theory become too great, it's schism time. If you don't stick to certain precise rules, or get funny ideas about ordaining women and put them into practise...you have a great problem with most of the traditional Theravada establishment. If you don't do your Ngondro preliminary exercises, you are not allowed to receive most of the empowerments and instructions for higher Yoga tantras etc. in the Tibetan traditions. The same would go for Japanese Buddhist traditions in different waysetc., although I agree that certain streams of Buddhism embrace syncretism more than others.
It is true that the different Buddhist traditions do not have a pan-buddhist inquisition in place that would excommunicate loads of people, burn witches etc. (thanks for that!!!). But all Buddhist traditions (right until the time they entered the western industrial world) are/were governed by highly detailed rule-systems. I am really glad that we as westerners have the opportunity to look for what is most fitting...but as a historical tradition Buddhism isn't half as liberal as most of us westerners would want it to be. Now of course we can claim to know that the essence of Buddhism is such and such and doesn't have anything to do with the cumbersome organised religions calling themselves Buddhist.
I know that I am repeating myself, but I will say it again. Zen is a Buddhist tradition. Take the cornerstones of Buddhism out of it and it ain't Zen anymore. It is a finger pointing at something that is beyond notions of religions (and is all of them at the same time). But not all fingers appear the same initially.
Most individuals growing up in a western consumerist society don't like rules that limit their personal freedom in any way. We are all used to shopping for what we want and discarding what we don't want.
Due to Buddhist traditions not being able to enact some kind of social peer pressure in the West, we often feel that that makes it such a freedom loving religious tradition. My own research and my experience of living in Japan tells me otherwise.
PPS - The Dalai Lama also said, "My religion is very simple. My religion is kindness." That is true, too.
...as for the Dalai Lama, whom I highly respect btw. ....just google Dorje Shugden controversy and stuff related to CIA covert warfare in Tibet....day to day life is a whole lot nastier than most of the Dalai Lama's coffee table book quotes ( no matter how true they might be on some levels).
May we all sentient beings realise the truth together.
Gassho,
Hans