On Ahura Mazda
Ahura means the Lord Creator, and Mazda means Supremely Wise. This was the name by which Zarathushtra addressed his God. He proclaimed that there is only one God, who is the singular creative and sustaining force of the Universe. Zarathushtra was the first Prophet who brought a monotheistic religion.
On Dualism
Even though there is only one God, our universe works on the basis of moral dualism. There is Spenta Mainyu or progressive mentality and Angra Mainyu or regressive mentality. Having given us the ability to choose, Ahura Mazda leaves us alone and allows us to make our choices. And if we choose good, we will bring about good, and if we choose evil, we will cause evil. This is how the moral universe operates.
Main maxims of Zoroastrianism
Humata, Hukhta, Huvarshta, which mean: Good Thoughts, Good Words, Good Deeds. There is only one path and that is the path of Truth. Do the right thing because it is the right thing to do, and then all beneficial rewards will come to you also.
Original article here.