Also known as Zarathustra, Zoroaster was the founder of Zoroastrianism. He was born in Azerbaijan, what was then known as Northern Persia. The exact date of his birth is unknown, but it is roughly estimated to be around the 7th century BCE. During his life, he received a vision from Ahura Mazda, the good god, of the reality occuring in this world. He was warned of an upcoming war, how people should live in this world, and other "truths" instructed by Ahura Mazda. Chosen to inform the world, Zoroaster spent the rest of his life spreading his beliefs throughout the Persian Empire. He struggled to persuade others to follow Zoroastrianism at first, but it quickly became one of the major ancient religion later on.
Darius the Great
Darius the Great was the third ruler of the Achaemenid Empire (around the 5th century BCE). He believed that his rise in power came from Ahura Mazda. During this time, Zoroastrianism had widely spread throughout the empire, and being the ruler of the kingdom, his faith influenced many of his people as well. Following Zoroastrianism's beliefs, he tried to live a life of peace, just, and righteousness. Darius also believed that rebellions, intruders, and general crimes were the works of Angra Mainyu, and he fought to bring peace and what is right back to the kingdom. His actions to help his empire convinced many Persians to support him, and by doing that, they also followed in his beliefs of Zoroastrianism as well.
Adashir founded the Sasanian Empire by defeating the Parthian army. Along with the then Persian Empire, Adashir also conquered other territories as well, such as Esfahan, Kerman, and Khuzestan. He established Zoroastrianism as the official Persian religion.
Karter was a Zoroastrian high priest also during the 3rd century CE, he wanted to get rid of the other religions practiced in Persia. He had many enemies that were of other religions, especially the Manichaeism founder, Mani. With the help of Bahram, the ruler at that time, Karter found a chance to put him in prison, where Mani eventually died there. Karter was very influential to the restoration of Zoroastrianism in Persia.