The nonduality of advaita vedanta is pretty different from Dzogchen, actually. Way different from Zoroastrianism.
How so? I'm quite ignorant on the differences. I didn't even know Zoroastrianism had a non-dual component.
Well, he linked up a pdf that has some newer ideas about Zoroastrianism and how previous scholars got things wrong. You can read that here if you want to: http://tenets.zoroastrianism.com/AManualofKshnoom.pdf
...I started it and it's pretty interesting, but I generally like to read about religion, anyway. Not sure why, but I enjoy it as a hobby or something. Anyway, Zoroastrianism is another religion where the goal is union with god or godhead, so its nonduality is similar to other theistic religions of that variety. And if I recall correctly it's theistic in the sense that "before the personal god there was a non-personal god, so it's not really god its nondual potentia, the inexhaustible source of all things". I must admit, this does seem a common enough idea in multiple religions.
From the PDF:
SPECIAL FEATURES OF THIS BOOK
(showing items of Essential Occult Knowledge of the Zoroastrian
religion taught in Khshnoom, not found in philology).
1. AHU and Ahura Mazda, the twofold concept of the Godhead
in Avesta - the former, impersonal, inconceivable, Absolute
One in oneness, refuting the century-old heresy of "Dualism"
as the fundamental theological Teaching of the Zoroastrian
Faith; the latter, (Ahura Mazda), the personal Deity, the creator
of the Universe, conceivable from his numerous names
occurring in Hormazd and Ram Yashts.
AHU, literally meaning, "it IS" (Only as it occurs in the Yatha
AHU Vairyo prayer) corroborates with "it IS" occurring in
pre-philological "Ethical Zervanism" which "starts squarely
with the unity of the godhead of which nothing positive can
be stated except that "it IS". God, the One, is pure
potentiality". ("Zurvan" p. 270 - Prof. Zaehner). Thus in
Zervanite Writings, though the true Avestan term AHU is
forgotten, its literal meaning, "it IS", survives.
2. Description of the Pre-Cosmo-Genesis World,. beginning with
_ AHU above mentioned showing manifestation of Ahriman
(first) and Ohrmazd (later), and other knowledge relating to the
creation of the Universe, and showing Where man came from
and Why, and What is the Ultima Thule of human existence.
Reminds me of Qabalah overall (not just this, but the rest of what I've read in the PDF). When I came to dzogchen from a qabalah background, I was convinced it was the same thing in different words, but now I really don't feel that way. It's funny because as I read this pdf, I think "sounds like qabalah" quite frequently, but don't think "that sounds like dzogchen," so that's pretty interesting because I haven't really studied or practiced qabalah for over 10 years now and dzogchen is really much fresher in my mind on a daily basis, so you'd think more things would sound like dzogchen to me than qabalah in this pdf. There's the AH in AHU having some connection with the sky/space and the vibratory colors, but so what, the qabalah had all that, too, and a lot more.
"Use what seems like poison as medicine. We can use our personal suffering as the path to compassion for all beings." Pema Chodron