Zoroastrianism, practised for much the same reason as Christianity, it is the precursor to the Abrahamic religions. Ahura Mazda(God) is a Benevolent and Omnipresent but not omnipotent, because of the problem of evil. Zoroaster was the prophet of the Ahura Mazda and performed many Jesus like feats, except 4000 years earlier.
islam
Prior to the conversion to Islam, the predominant religion of Persia was Zoroastrianism.
No religion is called old or modern religion. God religions are revealed by God and remains as assigned and commanded by God. The main religion of Persians is Islam.
Zoroastrianism or Mazdaism.
Zoroastrianism
Most Persians today are Muslim, but before the advent of Islam in Persia, most Persians were Zoroastrians.
Persians are practicing the religion of Islam.
Jeid
Most Persians today are Muslim, but before the advent of Islam in Persia, most Persians were Zoroastrians.
It is not true that Muslim Persians drink liquor. It is strictly forbidden; per Islam religion and Islam teachings in Quran and Sunnah; to drink alcohols. If some Muslims (Persians or not) don't follow Islam teachings then they are sinful and should repent.
ancient Persians
Islam (muslims)