Complex sentence: Mostly all Nawayaths are Muslims but during migration some of the nawayaths had become Zoroastrians.These zoroastrians then migrated to Mumbai (Bombay) and Gujrat and settled there.
Split into simpler sentences: Mostly all Nawayaths are Muslims but during migration some of the Nawayaths had become Zoroastrians. These Zoroastrians then migrated to Mumbai (Bombay) and Gujarat and settled there.