Zechariah alluded to God"s promise to raise up a horn, symbolic of strength, of salvation from David"s descendants (i.e, a mighty Savior, Psalm 132:17; cf. Psalm 18:2). He was not speaking of John but Jesus. Zechariah knew of Jesus" coming birth because of Mary"s three-month visit ( Luke 1:56). The other prophets in view are all those who spoke of the coming Messiah. [source][source][source]