You may see this post:

https://www.al-islam.org/ask/topics/76208/questions-about-Zoroaster

And here is an excerpt from Tafsir al-Amthal:

Who Magians Are: The word /majus/ (Magians) is mentioned in the Qur’an only once, and it is in this very verse. Regarding the fact that they are mentioned opposite to polytheists and in the row of those having Heavenly religions, it is understood such that they had had a Divine Faith, Book and Prophet.

No doubt that today the followers of Zoroaster in Arabic are called /majus/, or at least, the followers of Zoroaster form an important part of them, while the history of Zoroaster himself is not clear at all.

It is so ambiguous that some have recorded his advent in the eleventh century B.C. and some others have said that it happened in sixth or seventh century B.C.1 . This marvelous difference, viz. five centuries, indicates how dark and ambiguous the history of Zoroaster is.

It is known that he had a book by the name of, Awesta which was destroyed in the invasion of Alexander to Iran, and later it was written at the time of one of the Kings of Sasanian Dynasty.2

There have not been available so much matters from their belief, but what is more famous than all today is their belief in two origins of good and evil, or light and darkness. They consider the god of goodness and light as Ahura Mazda, and the god of evil and darkness as Ahriman.

They respect the four elements, and the fire in particular, so much so that they are called ‘Fire Worshippers’ and wherever they live there is also a fire-temple, large or small.

Some philologists believe that the term /majus/ (Magians) is derived from /mug/ which was used as a title for the leaders and clergymen of this religion, and the word /mu’bad/ which is now used for calling their clergymen had originally been derived from /mu‘wad/.

Some Islamic narrations indicate that they had been the followers of one of the Divine prophets but later they deviated from the path of Monotheism and turned to some blasphemous beliefs.

We read in some Islamic narrations that the polytheists of Mecca asked the Prophet (S) to take capitation from them and let them to worship idols. The holy Prophet (S) answered them he would not take capitation from anyone except the people of the Book. The polytheists wrote in answer to him (S).

“How do you speak like that while you have taken capitation from the Magians inhabited the region of Hijr?”

The Prophet (S) said:

“Verily Magians had a prophet, who was killed, and a Book which was burnt.”3

Another tradition from ‘Asbaq-ibn-Nabatah denotes that once Imam Ali (as) went upon a pulpit and said:

“Ask me before you are in lack of me.”

Then ‘Ash‘ath-ibn-Qays, a famous hypocrite, stood up and said: O’ the commander of the believers? How is it that capitation is being taken from Magians while there has not been sent down any Divine Book for them and they had not had any prophet?

Hadrat Ali (as) said:

“Yes, O’ ’Ash‘ath! Allah has sent down a Book unto them, and has appointed a prophet for them.”4

Imam Sajjad, Ali-ibn-il-Husayn (as) in a tradition said that the holy Prophet (S) said:

“Treat with them in the same manner that you treat with the People of the Book, and the purpose of the Messenger of Islam was Magians.”5

By the way, it must be noted that the Qur’anic term /majus/ is a plural form and its singular form in Arabic is /majusi/.6

3- Who The Sabeans Are: It is understood compendiously from the above mentioned verse that they have also been the followers of some heavenly religion, in particular that their name has been located here between the names of the Jews and the Christians.

Some commentators consider them as the followers of Yahy-ibn-i-Zakarriya whom Christians call ‘John the Baptist.’ Some others believe that Sabeans had taken a part of the belief of the Jews and a part of that of the Christians and mixed them, thus they think that their religion is something between those two religions.

Sabeans consider a great importance for water in their belief and, therefore, many of them live by the great streams. It is said that they also respect a few stars, and that is why they have been accused as star worshippers, though the apparent of the verse indicates that they are not in the row of polytheists