‘As far as I’m concerned if someone wants to call themselves a “Zen Buddhist” I will accept that, the same way I accept other people’s various chosen identities. I would expect a person who calls themselves a “Zen Buddhist” to regularly practice zazen and to be trying their best to follow the precepts. I’d expect them to know at least the basics of the philosophy & history of Zen Buddhism. On the other hand, I know people who call themselves “Zen Buddhists” and don’t do any of those things. I don’t bother arguing against them.
As far as beliefs, it really doesn’t matter. Buddhism is not a belief system. Having said that, I should add the caveat that there are forms of Buddhism in which they care very much what you believe. But in the Zen form of Buddhism beliefs are not considered to be very important. My teacher used to say, “I believe in the universe.”’(from Hardcore Zen)
I have a basic hesitation before calling anything ‘zen.’ I think that was one of the things I absorbed while training at Zen Center; while some people were very keen to attach labels and name things, those teaching there rarely, if ever, seemed to. That works for me (and I appreciate that it was called the Zen Center, and that I have tagged this post ‘zen’; the point stands).