Zen is the final flowering of all religious ascension. Religion and spirituality keep rising and rising. And its final flowering is the silence of Zen. Zen is what the Upanishads came at, the Buddha hinted at. From all of that, what you finally get is Zen. If by any chance you come across a form of Zen that is very ritual-oriented or practice-centric, then you can reject that as not being Zen. Then, you can simply say that practitioner does not know Zen and is misinterpreting.
Books by Acharya Prashant are available on AMAZON: