Hi Van,
I look at this much as some folks uniting Zen practice with their Christianity: If one can find the "common groundless ground" in one's heart, that is enough. In fact, belief in Amida Buddha and the Pure Land, and Messiahs and Heavens, are very much alike. As you say, Zen and Pure Land are very blended on the Asian continent, and in Japan, even such Zen folks as Uchiyama Roshi and D.T. Suzuki had a place in their lives for Pure Land practices.
Zen found many ways to harmonize the beliefs, basically coming down to: Inside is outside, outside is in, self power and the universe providing "other power" are not two, and the Pure Land is not somewhere "out there" for "out there" is "in here."
Here is a rather long essay about how that common ground was found doctrinally through the centuries. There are several historical reasons why the two ways tended to stay more separate in Japan:
https://web.archive.org/web/20100609...ure%20Land.pdf
For many, prayer is a kind of Zazen. Also, do you realize that our sitting Zazen is a kind of prayer? Yes, for sure, a prayer of gratitude in which nothing is asked, thus we sit.
I would let those who find Buddha in prayer just pray, for crossing the legs or pressing the palms together and bowing is not a matter of shape or form.
Dogen very clearly, in his many writings, was a rather traditional Buddhist fellow who believed in rebirth. I do not believe that he mentions the "Pure Land," but he does talk about "next lives" after the heart stops in this one. He also believed that one could see through all that and be liberated even in this life. Buddhists have found many solutions to what "gets reborn if there is no self," for example, our stream of Karma that is like a line of falling dominoes, there yet cannot be pinned down. Personally, I am agnostic and "let what ever happens happen" about rebirth, believing that the most important thing is to live good now whether there are next lives or not. I also see rebirth in every blade of grass and child's smile.
Gassho, J
STLah
Sorry to have run long