They will look on me, the one they have pierced, and they will mourn for him as one mourns for an only child, and grieve bitterly for him as one grieves for a firstborn son. (ESV Zechariah 12:10)
Most questions here centre on the sudden switch of pronouns in the Hebrew text, which one moment speaks of looking on “me”, God, and then mourning for “him”, someone else.
10 And I will pour upon the house of David, and upon the inhabitants of Jerusalem, the spirit of grace and of supplications: and they shall look upon me whom they have pierced, and they shall mourn for him, as one mourneth for his only son, and shall be in bitterness for him, as one that is in bitterness for his firstborn. (KJV)
It should be noted that a few manuscripts and translation depart from that reading and offer “him” or “the one” instead of “me”.
10 And I will pour out a spirit of compassion and supplication on the house of David and the inhabitants of Jerusalem, so that, when they look on the one[a] whom they have pierced, they shall mourn for him, as one mourns for an only child, and weep bitterly over him, as one weeps over a firstborn. (NRSV)
Nevertheless the 8th Century St Petersburg Hebrew codex and other early evidence for the Massoretic text stand with “me”, and by the principle that the more difficult reading is the more likely one, there does appear to be a subject switch from “me” to “he”.
23 By myself I have sworn, from my mouth has gone forth in righteousness a word that shall not return: “To me every knee shall bow, every tongue shall swear.” 24 Only in the Lord, it shall be said of me, are righteousness and strength; all who were incensed against him shall come to him and be ashamed. 25 In the Lord all the offspring of Israel shall triumph and glory. NRSV Isaiah 45:23-25)
It looks like the writer (speaking for God) is emoting of how in the past Israel had attacked God yet now, amazingly, they are looking to Him for help. So it’s an expression of love from Father to children and children to father. It’s poetic language that doesn’t need elaboration or apology.
Zechariah 12:10 as a prophecy of the crucifixion – John 19:37
The New Testament interpretation of Zechariah 12:10 is that there is an application to Jesus:
36 These things occurred so that the scripture might be fulfilled, “None of his bones shall be broken.” 37 And again another passage of scripture says, “They will look on the one whom they have pierced.” (John 19:36-37)
That in itself makes it natural to read back into the Old Testament and wonder if like the Immanuel prophecy there is some prior fulfilment in Zechariah’s own time.
And I will pour out on the house of David and on the inhabitant of Jerusalem a spirit of favor and pleading for favor. They will look to me.