Complex sentence: Many scholars argue that this collection originally consisted of three independent and anonymous prophecies, two of which were subsequently appended to the book of Zechariah (as what scholars refer to as Deutero-Zechariah) with the third becoming the book of Malachi.
Split into simpler sentences: Many scholars argue that this collection originally consisted of three independent and anonymous prophecies. Two were subsequently appended to the book of Zechariah (as what scholars refer to as Deutero-Zechariah) and the third became the book of Malachi.