I've heard about this in several places, but I can't understand how these two things can collocate with each other. These two philosophical systems are too different to be merged, aren't they?
( Sorry, I didn't notice you changed the content of your question completely.
Please read about him. His name is Hugo Makibi Enomiya-Lassalle, a German Jisuit, as well as a Zen Master ( of Soto-Shu group ). Since I am not or can not master all the core ideas of all groups of Zen Buddhists, let me answer with the assistance of Wiki ( mostly from my mother tongue's site. ( English Wiki is too short ))
According to the "source", he is considered one of the foremost and prominent and possibly the first one to have established Zen-Christianity as an organization ( kindly see the foundation he built in Switzerland ( sorry no English site ))
Firstly, be reminded he was a German citizen when Imperial Japan was an axis power at that time. So that he went there in order to spread Christianity by the order of Germany Jesuits.
From the source
Why Lassale became interested in Zen was because when he tried to spread Christianity, he considered he needed to know the Japanese thinking to the religion. In another words, "Before you teach, know the person".
Then after that ( from the source )
But as he actually started practicing Zen, he felt Zen has the same concepts that match with those of Christianity, namely, Meditation, Contemplation. He thought "abandoning" the "self" was the effective way and the "first stage" to acquire the "undoing one's soul receptively" "in order to receive the vision of God directly" in Christianity. He took the Zen's highly arranged methods through its long history to obtain the core idea was the most adequate path for the "materially affluent" modern people.
But his thought was,
Up until around 1962-1965, when the Second Vatican Council was held, his thought and his books, which tried to unite Zen with Christianity had not been welcomed by the orthodox Catholic church, even high ranking clergymen criticized him. But after around when the Council was held, his idea began to be gradually accommodated by people and criticisms began to vanish, he started spreading Zen-Christianity not only in Japan but broadly abroad too, especially preaching his ideas to Christians.
I am afraid what I can do is only around here. There are another explanations, but they are highly religious so that I will not be able to translate adequately probably ( since I felt the difficulty of the translation above. )
Have a nice day.