Are these the four directions?
Rashi: The Sarim of the early kingdoms, which rule in the four directions.
Radak: They are l'Arba Ruchos. Also "va'Yavo Yerushalayim" (Shmuel II, 20:3) is like li'Yrushalayim. I.e. these four chariots go to the four directions, i.e. to authorize the four kingdoms to rule in the four directions (corners of the world, i.e. the entire world, each in its time.
Malbim: Every kingdom encompasses the four directions. The four horses in each chariot hint to this.
Why were they "Yotze'os me'Hisyatzev..."?
Rashi: They came in front of Him, and He authorized them to rule.
Radak: This was Hashem's mission. He sent them for this, like "va'Yavo'u Bnei ha'Elohim Lehisyatzev Al Hashem" (Iyov 1:6).
