Someone wrote to ask me what "Ku" means in Japanese. I think Esho means this Kanji, Kuu, 空, empty air, sky, shunyata, emptiness.
https://jisho.org/search/%E7%A9%BA%20%23kanji
Some folks sometimes say that one must be an atheist to be a Buddhist. We have some Christian and Jewish folks (also a couple of Islamic folks) who come practice with us. When this topic comes up, I say that one can practice Zen Buddhism while also a political liberal, conservative or apolitical, baseball fan or football fan or no sports fan at all, Catholic, Jewish or Muslim, Atheist or Agnostic. I would say that, so long as it is a belief system that avoids hate, violence, excess greed and such (e.g., a "Zen Buddhist Nazi" will go a dark way), all can mix.
Also, Some forms of Christianity and Judaism or other belief may be practiced in ways that shut out or are incompatible with other systems such as Buddhism (due to the problem of rejection and exclusivism on the other side ... "Jesus is the only way, meditation is evil" etc. ... not on the "Zen" side), but not all Christians and Jews practice in such ways. Some ways of practicing Christianity and Judaism are quite compatible and harmonious with Zen Practice. Some have a unnamed, open vision of deity that could be "Kuu 空". Sure.
People sometimes say that Buddha was an atheist. From my reading on the question over the years, it is more that he simply did not express an opinion on the subject as central to his Teachings, one way or the other. Further, he was addressing the system of gods in Indian religion, which was a bit of a different way of things. More here:
http://buddhism.about.com/od/basicbu...dhaatheism.htm
Zen is no more impacted by whether there is a "God" or no "God" than it is impacted by whether there is a table or no table in the same room where you sit Zazen. In either case ... table/no table or God/No God ... the sitting is the same. That is because we always sit as "what is" ... and if there is a table, that is "what is. If there is no table, that is "what is".
I often say ...
If there is a "God" ... whether in the Judeo-Christian way or some other, whether named "Allah" "Jehovah" "Thor" "Brahma" or "Stanley" ... I will fetch water and chop wood, seeking to live in a gentle way, avoiding harm to self and others (not two, by the way).
If there is no "God" "Allah" or "Stanley", or any source or creator or point to the universe at all, I will fetch water and chop wood, seeking to live in a gentle way, avoiding harm to self and others (not two, by the way).
In China, Vietnam and Korea for 1000 years (less so in Japan for historical reasons), many folks practice forms of Zen Buddhism mixed with prayers to Amida Buddha (a savior figure surprisingly like Jesus in many many ways) who promises to take the faithful to the heavenlike "Pure Land" when they die, and also to other saintly figures like Kannon and Jizo who may lend assistance to those in this world in need.
That about sums up my view, I am pretty agnostic on the whole topic ... happy to chop and fetch. I am not a big fan of "cosmic consciousness" ideas that are too simple.
Gassho, J