Could be an interesting idea, but I'm not sure religion played such an important role in creating unrest during EB timeframe. I think since they are not monotheistic religions they were more tolerant to each other with less zeal and fanatism than we encounter in later periods where monotheistic religions dominate the world.
Second point is that Seleucids can't be considered Zoroastrian as the were Hellenistic kingdom (with non-Hellenistic population). I'm not sure Zoroastrism even existed at that period. I think it appeared much later. Ptolies are Hellenistic kingdom too with Egyptian population. This makes the religion issue even more complicated as religions were interweaving a lot those times.
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