This essay wants to demonstrate that the verb "pasah" in Exodus 12 should not be translated as "pass over" but "hover over." This image is the same as Genesis 1:2 where the metaphor is used to compare the Creator-Spirit to a bird hovering over the deep-and-darkness. Kline provides some background for the use of avian imagery for God and his angels.
It seems as if Zechariah 6:9-15 forms a distinct section in the structure of the book. Kline addresses the question of the precise role of this passage in the structure of the book and this takes him to make a proposal on the overall structure of Zechariah.