In Zechariah's vision of four chariots in chapter 6 of his book, an angel tells him that the chariots are going to go to the "four winds of heaven," (verse 5)—in every direction. However, in verse 6, the angel says that two of the chariots are going north, and one south, and the fourth chariot is not mentioned at all! What happened to the fourth chariot? Why did two go north? What is going on here?
Before explaining the meaning of the chariots and the direction they take it would be could to identify why they are ‘going out to the four winds of heaven, after presenting themselves before the LORD’. As this part is not fully explained within the text it would be helpful to refer to similar ideas in the Bible:
With these references in mind it seems that the four winds in the Bible are often associated with the providence of God that are before the Lord and go out under the agency of angels. God sends out His providence and sovereignty in employing his angels between heaven and earth, as his servants for the accomplishment of his pleasure. This he does all over the earth (N,S,W,E) wherever the wind blows. This is certainly the meaning for in Daniel this ministry of angels make the waters rage and bring for the four empires from the sea which in Revelation 17:15 are ‘peoples, multitudes, nations and languages’ or the Gentile world. This providence under the agency of angels is further confirmed by the very nature of angels.
This must be on account that the angels are spiritual, agile, powerful, quickly and accomplishing the work that is appointed to them and is wrapped up in the providential workings of these four kingdoms.
I assume the direction is the direction the kingdoms first took, or a significant direction, but then they ‘patrolled the earth’ that is they went all over. I would have to look at a map, but considering that the four chariots were probably Babylon, Persian, and Greek and then Roman.
The Babylon (Red) needs ‘no mention’ as that was already history past. Persian going north must be the direction that the Persian expansion started. I just looked for a map and yes this is true, see here.
The Greeks (White) must have also expanded into the same region, because they overtook the Persians (Black). These kingdoms in the north (Persian and Greek) removed the Babylonians and kept them removed, which is why it set ‘God’s spirit at rest’. For as this freed Israel so they could fall back into line with God’s providential outworking of the Davidic kingdom and preparation for the Messiah. The Romans are not really considered in relation to restoring Israel as it was the Persians who did that, the Greeks are only included because of the suddenness of the conquest that Alexander made (represented as a leopard in Daniel 13:2 with regard to this speed). The Greeks can be said to have been ‘directly following the Persians with great speed’, or ‘the white ones go after them’. Thereby the Greeks solidified the establishment from exile from the Babylonians, whereas the Persians were the principle cause for that restoration. The Romans sort of start a new Chapter and their Kingdom is so strong and last so long that we treat them somewhat independently for the first three.
All that is left is to understand how the Romans (dappled, or patchy) would be the ones going south. This seems easy to confirm. Italy is definitely the most Northern of the four kingdoms so they moved south to conquer the entire Greek kingdom.
I think we underestimate how clear that the beasts in Daniel and also these chariots are these four kingdoms. The reason is that before the Babylonians there really was not a great kingdom in this region, and then each one was taken by the next until the Roman Empire gave sway to be the greatest kingdom ever to be in the world until that time. The fact that Christ was prophesied to come during that kingdom and then virtually demolish it, which did happen when Christianity first took over Rome, is both amazing and factual.
The reality of the constant overturning of Kingdoms from the Babylonians until Christ, was so new to the world, and must have been so tumultuous among the people that it is as thought the world was in birth pangs to receive its Lord. Meanwhile the world had reached its pinnacle in wisdom and learning from the Greeks and strength from the Romans, so when the resurrected Christ came in power by His spirit and overturned the world, it shows that the world had come to an end.
Christ came not just at the perfect time to fulfill the Law, but the most perfect time to destroy the world as well. His kingdom reigns. This is what the four chariots eventually established a place for, His throne. A throne that fulfilled the mountain of the Law, on which Moses received it, and raised up the new mountain, carved out of the first one, destroying the world.
Not "in all directions"
From the Av there is no sense that they are going in all four directions, but that God is the "Lord of all the earth".
The red horse
The meaning of the missing red horses is that there is no more judgement. Christ has removed judgement from the word of God.
Paraphrase: I understood the spiritual meaning, there were four revelations coming out of the cross, and the cross was a mixture of earthly and heavenly.
Paraphrase: The first testimony was strength over the flesh, and the second was strength in the mercy of the new birth.
Paraphrase: The third message was strength in Holiness. and the fourth message strength in the body of Christ (the church, as the mottled flocks of Jacob)
The four spirits are just another phrase for the four revelations or testimonies of God through the four voices.
Grace and Holiness return to heaven The mixture of grace and holiness remains on earth. Christ is the one who reconciles Grace and Holiness on the Cross.
The bay horse is a mixture, in one sense Christ and in another the church. They remain on earth as his witnesses.
The horses representing Holiness and Grace have been reconciled and heaven is at peace.
What of the red?
We determined tentatively that red was the color of sin and the judge of sin.
Since there is no red horse remaining, it means that judgement has ceased. Sin has been removed. This is a parallel prophecy to judgement being removed from the word as the axe head was removed from the water, and the water was turned to wine.
This exposition adds to the confirmation of the interpretation in the linked answer on colors.
The horses are INSIDE the chariots, carried by the chariots.
The chariots are not drawn by the horses. The chariots release the horses and the horses go the directions described.
ב מרכבה = in chariot
UFOlogist's or Star Trekker's view (disclaimer: I am not ufologist but I do like Star Trek):
The four mother ships carried little horse-like transport vehicles.
Four battleships carried torpedoes that were shot out in the described directions.