Answer: While the sentence structure in Zechariah may appear confusing, it must be remembered that we are dealing here with an English reproduction of biblical Hebrew with its peculiar usages.

In the context of Zechariah 12 we are told that God will defend His people and destroy their enemies. On that day, "they [the nation of Israel, i.e., the house of David and the inhabitants of Jerusalem, mentioned at the beginning of verse 10] shall look to Me [God] whom they [the nations, spoken of in verse 9, that shall come up against Jerusalem] have pierced; then they [Israel] shall mourn for him [the slain of Israel as personified by the leader of the people, the warrior Messiah who will die in battle at this time]."

Of course, God cannot be literally pierced. The idea of piercing God expresses the fact that Israel stands in a very special relationship to God among all the nations of the earth. God identifies with his people to the degree that He takes part figuratively in the nation's destiny. To attack (pierce) Israel is to attack God. That is why God says: "Me whom they have pierced" even though it is the people of Israel and not God who is actually "pierced." Accordingly, Isaiah says of God's relationship to Israel: "In all their affliction He was afflicted" (Isaiah 63:9), and in Psalms 83:2-6 we see that the nations which hate God manifest that hatred by seeking to destroy the Jewish people.

Christian commentators, in their confusion, equate the "Me" with the "him" of verse 10 and refer both to Jesus. Grammatically, the "Me" and the "him" cannot refer to the same individual. The only admissible interpretation is, as stated above, that the Gentile nations shall look to God, whom they have attacked by the persecution, death, and general suffering they inflicted on the nation of Israel ("him"), whose dead will be mourned by the surviving Jewish people. The rabbis of the Talmud saw this suffering personified in the leader of the people, the warrior Messiah, the son of Joseph, who will be slain at this time (B.T. Sukkah 52a). The entire nation's dead will be mourned, but the mourning over the death of the warrior Messiah symbolizes the collective grief as the people mourn for the fallen of Israel. The author of the Gospel of John realized the untenability of the claim that Zechariah's prophecy referred to Jesus. John, perplexed by Zechariah's prophecy, changed the wording of verse 10 to make it conform to his belief. Thus, he wrote: "They shall look upon him [not "Me" as in the Hebrew text] whom they have pierced" (John 19:37). Emending a text may be a convenient way of demonstrating one's theological beliefs, but has nothing to do with biblical authenticity.