My answer is for which you raised the question concerning my statement, would suffice.
Shunryu Suzuki would elaborate Zen as formal practice, informal mind.
I prefer Zen*******'s
I haven't got a clue what you're saying, sorry.
Of course, there is a separation between Zen as a school of Buddhism and Za-zen as a meditation technique. I believe that in Japan there is a rule that there are no Buddhist ceremonies conducted in the meditation hall, nor are there any religious symbols. I have an old book on the subject written by a Jesuit priest who settled in Japan. He wrote that when he went for training, the monk told him that practicing Za-sen would help him get a better understanding of Christianity and that, to his surprise, turned out to be the case.
There will normally be an altar with a Buddha image in the meditation hall, either Shakyamuni or Manjushri. But it's true the main ritual hall will be separate if possible.
As for the rest, yes. Zen is a practice that anyone can do. Our teacher, when he was recommending that people take part in a refuge ceremony that the visiting abbot of Dharma Drum would be performing, said that even Christians should feel free to do it, since becoming a Buddhist would make you a better Christian. I didn't understand at the time and even thought it sounded wrong, but now I think I get it, and it's true. It's not
just the meditation, since that's just part of the holistic package, but the meditation is a gateway for a lot of people, including Christians and Jews. Then their view of their original religious tradition will probably shift and grow more nuanced, but that's not necessarily a bad thing (although some of their co-religionists may not accept it).