Then I turned and raised my eyes and looked, and behold, four chariots were coming from between two mountains, and the mountains were mountains of bronze. Zechariah 6:1

Once again we see the expression “raised my eyes” which means Zechariah is receiving a prophetic message from God. Now the first clear thing here is the parallel to the 4 horsemen in Revelation, (reference Revelation 6:1-8) This vision is clearly about the 4 horsemen, the 4 spirits from God that are bringing judgement upon Israel until the Millennial Kingdom is setup with Christ 

And I looked, and behold, a white horse. He who sat on it had a bow; and a crown was given to him, and he went out conquering and to conquer. Revelation 6:2

Another symbol to point out there is the 2 bronze mountains, bronze is symbolic of judgement in the Bible, and the two mountains are most likely Mt, Zion and the Mt, of Olives, where Christ will return 

And in that day His feet will stand on the Mount of Olives, Which faces Jerusalem on the east. And the Mount of Olives shall be split in two, From east to west, Making a very large valley; Half of the mountain shall move toward the north And half of it toward the south. Zechariah 14:4

With the first chariot were red horses, with the second chariot black horses, with the third chariot white horses, and with the fourth chariot dappled horses—strong steeds. Zecharian 6:2-3

The color of the horses is revealed, again similar to Revelation 6:1-8, Red is typically symbolic of blood/war/judgement. 

4Then another horse went forth. It was bright red, and its rider was granted permission to take away peace from the earth and to make men slay one another. And he was given a great sword. Revelation 6:4

The black horse is symbolic of death/famine.

Then I looked and saw a black horse, and its rider held in his hand a pair of scales. 6And I heard what sounded like a voice from among the four living creatures, saying, “A quart of wheat for a denarius,a and three quarts of barley for a denarius, and do not harm the oil and wine. Revelation 6:5-6

 Now the good news is white is typically symbolic of peace and victory, where in Revelation 6 we see the white robes of the martyred saints.

11Then each of them was given a white robe and told to rest a little while longer until the full number of their fellow servants, their brothers, were killed, just as they had been killed. Revelation 6:11

Probably the most mysterious of the symbols is the dappled horses, which appear to be a blend/mixture of many things. This could represent a combination of judgement, such as war and famine, or it could be symbolic of the gifts of the Holy Spirit among Gods messengers. Its a strong force that will bring victory to Christ’s Kingdom

Then I answered and said to the angel who talked with me, “What are these, my lord?” And the angel answered and said to me, “These are four spirits of heaven, who go out from their station before the Lord of all the earth. Zechariah 6:4-5

Once again Zechariah asked the question , “What are these”? And  messenger explains them for us, “These are four spirits of Heaven” So the Four Horseman , these 4 Spirits are sent by God to fulfill his Will and purpose

The one with the black horses is going to the north country, the white are going after them, and the dappled are going toward the south country.” Then the strong steeds went out, eager to go, that they might walk to and fro throughout the earth. And He said, “Go, walk to and fro throughout the earth.” So they walked to and fro throughout the earth. Zechariah 6:6-7

God’s judgement will be to the entire world, “throughout the Earth” However remember a few things, God is in complete control (Psalm 46:10) and we have Victory in Jesus Christ (1 Corinthians 15:57)

And He called to me, and spoke to me, saying, “See, those who go toward the north country have given rest to My Spirit in the north country.” Zechariah 6:8

This is such a beautiful way to end this vision, despite all the judgement and turmoil, Gods Spirit is still at rest, we can have true Rest and peace in Christ, because Christ has already overcome the world (John 16:33)