Zen could be understood as a more refined version of Buddhism in the sense that if you burn away all the excess, Zen is what remains. Zen has no religious doctrines, but it does not deny that these exist either. It doesn’t seem to have the iconic Buddhist teachings of karma, reincarnation and nirvana, at least not with the clarity that these appear in other Oriental systems. Zen goes beyond logic and outside of logic. The only thing that Zen teaches is how to teach yourself. It transcends doctrines so that the category of doctrine is irrelevant.
https://orthodoxreflections.com/can-zen-buddhism-fit-within-orthodox-christianity-a-research-project/