We will assume that you are referring to Zech 1:18-21.

Zech 1:18-21  "Then lifted I up mine eyes, and saw, and behold four horns. And I said unto the angel that talked with me, What be these? And he answered me, These are the horns which have scattered Judah, Israel, and Jerusalem. And the LORD shewed me four carpenters. Then said I, What come these to do? And he spake, saying, These are the horns which have scattered Judah, so that no man did lift up his head: but these are come to fray them, to cast out the horns of the Gentiles, which lifted up their horn over the land of Judah to scatter it."

In verses 18-21, Zechariah beheld four horns and four carpenters. In the Scriptures, a “horn” is a symbol of power (whether on an altar, on an animal, or used figuratively), and a “carpenter” is a symbol of one who builds up. Therefore, the four horns in this vision are four powers, but what powers? The effect of these powers was to scatter (punish) Judah, Israel, and Jerusalem. The implication in verse 21 is that Gentile powers did the scattering. 
In this particular context, the sequence is Judah, Israel, and Jerusalem (the city). Judah, the southern kingdom was scattered by the Gentile powers of Egypt and Babylon. With Israel, the northern kingdom, the scattering Gentile powers were Assyria and Syria. But since the Old Testament prophecies are written for the Christian’s admonition, it is likely the primary application pertains to a greater picture with a different starting point than either Egypt or Assyria.
The four universal empires listed in Scripture are Babylon, Media-Persia, Greece, and Rome. Consider King Nebuchadnezzar, an enemy of Israel, who was called a “lion” that would come down from the north and scatter Israel (Jer. 4:7). God also called him “my servant” (Jer. 25:9). Nebuchadnezzar was permitted to come down against Israel to destroy Jerusalem and Solomon’s Temple because of the nation’s previous disobedience and waywardness. And even when Cyrus, the king of Persia, allowed the Israelites to go back to their homeland, they were a subject people.  Therefore, these four horns in Zechariah most likely picture the four major Gentile powers, or empires, starting with Babylon and corresponding with the image in the second chapter of Daniel. After Babylon was Media-Persia, then Greece, then Rome.