The black horses which are therein go forth into the north country; and the white go forth after them; and the grisled go forth toward the south country.
The black horses which are therein go forth into the north country - Babylon (note Jeremiah 1:14). The North is the quarter specified in particular whence Judah and Israel are hereafter to return to their own land (Zechariah 2:6; Jeremiah 3:18). "The black horses" go to Babylon, primarily to represent the awful desolation with which Darius visited it in the fifth year of his reign (two years after this, prophecy) for revolting (Henderson). The "white" go after the "black" horses to the same country: two sets being sent to it because of its greater cruelty and guilt in respect to Judea. The white represent Darius' triumphant subjugation of it (Moore). Rather, I think, the white are sent to victoriously subdue Medo-Persia, the second world-kingdom, lying in the same quarter as Babylon-namely, north.
And the grisled go forth toward the south - i:e., to Egypt, the other great foe of God's people. It being a part of the Groeco-Macedonian kingdom, stands for the whole of it, the third world-kingdom. Perowne (Smith's 'Bible Dictionary') less probably supposes the reference to be to the subjugation of Egypt (called Mudraja), which had revolted from Darius I. (according to recently deciphered inscriptions.) The weakening and overthrow of the Persian empire was, in this view, regarded by Zechariah as the forerunner of the setting up of the kingdom of God. But, if so, Zechariah would have 'anticipated' that which the result did not warrant. The believer's conviction that "all scripture is given by inspiration of God" confutes at once such rationalistic interpretations.