Yoga and Zen in the modern world are seen as direct perpendicular paths, one focusing on the body and the other on the Mind. Nothing could be more diametrically wrong than this perception of duality.
Yoga at its root is a concept of aligning the body with everything that we are doing at that moment. It could be listening to music, reading a book or any action that we are occupied with in a given moment. It is called nada, gnana, hatha and Karma yoga respectively. Yoga requires its practitioners to concentrate on whatever you are doing without any other preoccupation.
Zen puts it very simply- No dithering. So there is no difference between the two disciplines except in training. Zen was born in a simple moment in the vulture’s peak when the teaching was transmitted from the mind of the Buddha to Sariputra, the first Patriarch.
Yoga was born in an earlier era before the Buddha during the time of sage Kapila as Samkhya Yoga. In the Light of Asia by Edwin Arnold, the education of the historical Buddha under sage Vishwamitra is described where the Buddha shows his ability to count to the infinite and infinitesimal levels.
Samkhya Yoga is the Yoga of numbers, the description of nature in terms of the number of its constituent elements. So the two disciplines are intertwined at birth, only Zen had to wait for its transmission as the intuitive element of yoga, the wordless teaching of the ultimate.
Patanjali encoded the system of yoga in his Patanjali Yoga Sutra – Aphorisms of the truth. While comparing the two systems of Buddha and Patanjali, the famous Vipassana teacher, Sri Satya Narayan Goenka said that only a few of the aphorisms conflicted with the teachings of the Buddha and these related to the discipline of breath control. Buddha did not advocate any breath control. So it is postulated that these aphorisms were later day additions not authorised by Patanjali.
So Zen and Yoga share the same roots and they can be considered part of the same system of thought only that Zen was a progression of the earlier system. Acharya Nagarjuna was one of the progenitors of the Zen system and its core logic. Acharya Nagarjuna in his own way described logic as a nihilistic system where the truth is arrived by denying everything.
Zen shares this philosophy but goes to the practical realm using impossible koans to tease the mind into silence and long meditation sessions of Zazen to silence the body. Zen is an indirect approach to direct seeing of the mind. It involves developing mindfulness and concentration over long hours just to enjoy the nothingness, the silence.
Yoga is more active and though some of the schools focus on meditation, the approach is always to attain a state of being, a feeling of devotion as in Bhakti yoga, or Knowledge when we learn more. Yoga is meant to see the reality of life, to experience the pain in the joints when we reach the right hatha yoga pose or feeling elation when we are in the thrill of the Lord. Yoga focuses on Union with the nature of the thing that is being concentrated upon.
Seeing God is the thrilling feeling of revelation when the haze is cleared and Glory is revealed. Knowledge happens when the clouds of ignorance are cleared to reveal the light. Music is fun when the listener melts in the music and totally identifies with it. Yoga is this state of being.
Zen comes to this state by revealing the nothingness that is shared by every object in the nature, you included. When we know that the music of the flute arose in the nothingness inside the flute. When we know that after knowing everything, we are still ignorant. When we know that you and God are melting in this nothingness. That this nothingness is the only truth…
Zen reveals everything in the nothing. Yoga asks us to identify with everything but both say the same thing, that is, to enjoy the present moment. Now it is for you to choose your state…
– by Srinivas Reddy