You seem to ASSUME yourself that Zaratushtra wrote poetic songs whose lyrics were to be interpreted as literal facts about existence and then to be followed blindly as such by all of humanity for the rest of history no matter what conclusions about existence all forthcoming humans may reach using their very own sacred minds.
Somehow I find this assumption a lot less Mazdayasna then the belief that Zarathushtra wrote beautiful and educational poetry to teach people to think critically for themselves since he believed that the thinking itself was the sacred activity, not the endless interpretations of his texts. Zarathushtra was interested in DIALOGUE with friends, not in bending the knees of loyal blind followers.
The important question is not what Zarathushtra thought and meant, the important thing is what you and I think and mean. That's what Zarathushtra thought, at least... He never asked you to obey him blindly, that's what Muhammed and Jesus wanted us to do, but not Zarathushtra. And THAT is the big difference in Mazdayasna compared to Abrahamism.
I am afraid that you are ASSUMING that Zarathushtra is saying that
reality just APPEARS to be dualistic, As to he not saying that it is
dualistic, let me just say the following:
It simply stretches credulity to think that man who develops a
theology in which there is :
1. A bridge into another existence, which is reached only after death
by 'selves' that must conform to certain criteria in other to cross
2. Who repeatedly postulates a states of existence such as the Abode
of Mazda, the House of Song, the House of best Mind, etc, which are
at the very best only partially accessible this i side of Completion
a Completion ( haurvatat) that when fully achieved makes one cross
Over the said Bridge and NEVER EVER mentions that this is imagination
or specify anything about this material reality being the only one.
Can then be said, to postulate anything but dualism
And the claims of Monism are NOT scientific they are philosophical
Monism is not subject to scientific method verification techniques
any more than any other philosophy is. So your argument from Science
is immaterial as top both Zarathushtra and monism. We can only go
from what the man said not from what we may think he had to say or
meant to say but did not say. If we were to argue from such a
position, then we will be arguuing from wishful thinking assuming
which of courser can me an ass of u and me.
But enough I am not going to convince you and you certainly are not
going to convince me , so its pointless