What do the four horses in Zechariah symbolize?

In Zechariah 6, the four horses pulling the chariots are interpreted as the four spirits of heaven, which signify God's angels going forth to accomplish His will on earth. This illustrates the active role of divine beings in fulfilling God's purposes, including the spreading of His gospel. The different colors of the horses—black, white, red, and grizzled—depict various aspects of God's judgment and grace as these spirits move throughout the earth. This imagery reminds believers of the spiritual battles taking place and the providential care of God in overseeing those efforts.