Wrote to Raan:
You're implying that emptiness of phenomena leads to Self, and I can certainly see where you might get that impression -- Advaita Vedanta (both traditional and neo) might say things like the world is illusory and eventually subsuming the world to be Brahman - pure Subjectivity.
Emptiness teachings do not do such a thing -- we do not subsume nor reduce one pole to another -- whether Object into Subject, nor Subject into Object. By saying X is empty, we do not therefore imply that only Y is real. This is precisely why its called Nonreductive Nonduality -- we do not reduce everything into one thing. By seeing the emptiness of Self, we realize 'Self' is merely a conventional label collating the conventional parts, aggregates, and dependencies, empty of any intrinsic self/Self/agent behind or within those phenomena. By realizing the emptiness of phenomena, we liberate our clinging and notions of inherent existence or absolute arising/abiding/subsiding of phenomena, revealing the world to be mere conventional reality and play of intricate interdependencies, non-arisen, illusory yet vividly appearing. Conventionally table is still table, you are still you, he is still he, only the inherent view is seen through. We do not subsume all conventional realities into One absolute, ultimate X. This is all very different from saying "There is only X [Self/object/The Absolute/Awareness/This/Brahman] and no other", or "You are Me, I am You".
And it is not the case that Madhyamika does not focus on the emptiness of Self... you might want to read Chandrakirti's analysis of the chariot in relation to self and aggregates? The same emptiness of self is applied both to the subject/agent/person as well as all dharmas and phenomena. It came to be known as "twofold emptiness". As Greg Goode wrote in http://nonduality.com/goode6.htm -- "In Middle Way teachings, it is said that without realizing the selflessness of persons, it is not possible to realize the selflessness of phenomena.[2] So the meditative reasonings are done first on persons."
Therefore, Madhyamika is thoroughly nonsubstantialist, nonreductive, non-subsuming, non-reifying kind of teaching. Prasangika Madhyamika is definitely like that. (Can't say the same for certain interpretations of Madhyamika such as Shentong, which in its more extreme forms are essentially no different from Vedanta teachings, however Shentong is still a minority view in Vajrayana and most Vajrayana practitioners take Prasangika view to be definitive. It is also my understanding that Shentong takes other non-Madhayamika views like the Yogacara or Tathagatagarbha teachings as definitive)
On the other hand, I think Zen (as well as Vajrayana and even to some extent Theravada) is a very mixed bag. I have found some Zennists to be very substantialist, and some Zennists to be very nonsubstantialists, and of course there's always room for views that are somewhere in between. In my impression, Linji the founder of Rinzai in China was in fact emphasizing more on the I AM -- you can find many quotes by Linji talking about the formless Self ("If you want to be free, Get to know your real self. It has no form, no appearance, No root, no basis, no abode, But is lively and buoyant. It responds with versatile facility, But its function cannot be located. Therefore when you look for it, You become further from it; When you seek it, You turn away from it all the more. - Linji ").
But the founder of Soto Zen -- Dogen -- was more of a nonsubstantialist kind, rejecting all notions of a changeless Absolute and explaining Buddha-nature in terms of non-self, impermanence and interdependencies. Japanese Rinzai Zen is based on Hakuin the father of Rinzai in Japan, who seems to be teaching nondual but I'm not sure if his view is as nonsubstantialist as Dogen, never studied too deeply into Japanese Rinzai.
That being said, of course, there are also adherents of Soto Zen that hold a very substantialist view. And certainly some of the predecessors of Dogen could have held a substantialist view? (I do not really believe in the 'unbroken lineage of the same realization' thing). It all depends on the individual.
A small excerpt from http://awakeningtoreality.blogspot.sg/2012/06/emancipation-of-suchness.html explains the view of Soto/Dogen:
"In studying the fasicle Bussho, we find that Buddha-nature is not a thing that represents some kind of foundation. Buddha-nature is impermanence and interconnectedness. It is essentially empty. Dogen breaks down the “thingness” or solidness of all things by deconstructing time, space and body. He only writes of the whole body or entire being, and the total functioning or interconnectedness of life. The temporal conditions are the coming together of all the factors which produce the formation of this very moment. That formation itself is Buddha-nature."
WoW that was fantastic. nice man!