Qur’an on Magians:
22:17: « Verily, those who believe (this revelation), and those who are Jews, and the Sabaeans and the Christians and the Magians and the polytheists – verily, Allah will judge between them on the Day of Resurrection. Indeed, Allah is Witness over all things. »
Note that the Magians are mentioned separately from the polytheists. If they were full-fledged polytheists, why would they be named separately along with the Christians, Jews and Sabaeans?
Hadith on Magians:
“Whoever kills a mu‘ahid (a non-Muslim living under Muslim rule) will not smell the fragrance of Paradise, although its fragrance may be detected from a distance of forty years.” Sunan Ibn Majah, Book 21, Hadith 2788
“Whoever oppresses a dhimmi or loads a work that is over his strength or takes something away from him by force, I am his foe on the Day of Judgment.” Abu Dawud, Kharaj, 31-33
“By Allah, he does not believe; by Allah, he does not believe; by Allah, he does not believe.” It was said: O Messenger of Allah, who is that? He said: “The one whose neighbour is not safe from his annoyance.” Sahih Bukhari, Volume 8, Book 73, Al-Adab, Number 45
Umar ibn al-Khattab mentioned the Magians and said, “I do not know what to do about them.” Abd ar-Rahman ibn Awf said, “I bear witness that I heard the Messenger of Allah, peace and blessings be upon him, say, ‘The Sunnah [to follow] with them is the [same] Sunnah [as for] the People of the Book.’” Muwatta Malik, Hadith 619
i.e., Zoroastrians are to be treated the same as Christians or Jews. As for the Sunnah with Jews and Christians, this is exemplified in the agreements the Prophet PBUH made with Christians: http://www.covenantsoftheprophet.com/. A historical example of this Sunnah being followed reasonably well in the centuries after the Prophet is Muslim Spain.
However, the Sunnah for militants is different. The Jews broke their agreements with the Muslims and formed military alliances with polytheists against them, so the Sunnah with these militant Jews involved defeating them and expelling them from the land so Muslims and Christians could live in peace and safety.
**Disclaimer: I am not a true scholar and am not proficient in Arabic. However, the last hadith cited and the Quranic verse are crystal clear. Though some of the hadith cited may be weak, the last one is Mutawatir, which is to say virtually infallible due to the great number of ear-witnesses who narrated it.