Unity of Ahura Mazda
Despite divine attributes, Ahura Mazda is fundamentally one.
Though described through various attributes and Amesha Spentas, Ahura Mazda is fundamentally one unified deity. The attributes are aspects of one divine reality, not separate gods. Zoroastrianism is essentially monotheistic.
Mazda is one, though known through many names.
Zarathustra's original vision was essentially monotheistic.
Zoroastrian Theology