how monotheistic is Zoroastrianism.?

i was reading the Zend Avesta's and some aspects of them seem polytheistic.

I think they're more dualistic.

Zoroastrianism was the first monotheistic religion on the planet---don't forget God has 22 names in the Old Testament.

Zoroastrianism is dualistic, wherein there are two opposing forces that govern the universe. In this case, those forces are Ahura Mazda and Ahriman. The former was the Creator; a god of light, fire, and good, while the former was the Ahura Mazda's antithesis; the god of destruction, evil, chaos, and darkness. There are certainly similarities between Zoroastrianism and the monotheistic Abrahamic religions, mainly because there are enough dualistic influences in Judaism, Christianity, and Islam that they are only sort of monotheistic. I know Christian theologians hand-wave Christian dualism by saying that God is actually more powerful than Satan, and only allows him to exist as a pawn in His plan.