Adam Clarke on Zechariah 1:20

Four carpenters - Four other powers, who should defeat the powers intended by the horns. These are the same as the four chariots mentioned Zac 6:1-3, Zac 6:6, Zac 6:7. The first was Nabopolassar, father of Nebuchadnezzar, who overturned the empire of the Assyrians. The second was Cyrus, who destroyed the empire of the Chaldeans. The third was Alexander the Great, who destroyed the empire of the Persians. And the fourth was Ptolemy, who rendered himself master of Egypt. Some of these had already been cast down; the rest were to follow. Calmet gives this interpretation, and vindicates it at length.