Zechariah 12:10 does have fulfillment in the 1st century, specifically with the death of Christ
zechariah 12:10 And I will pour out on the house of David and the inhabitants of Jerusalem a spirit of grace and pleas for mercy, so that,
when they look on me, on him 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.
John 19:34-37
But one of the soldiers pierced his side with a spear, and at once there came out blood and water. He who saw it has borne witness—his testimony is true, and he knows that he is telling the truth—that you also may believe.
For these things took place that the Scripture might be fulfilled: “Not one of his bones will be broken.” And again another Scripture says,
“They will look on him whom they have pierced.”
I guess, how is it not supported? The original context of the prophecy is in regards to the nation of Israel and their tribal clans mourning because they pierced God. Zechariah 12:12 is not about the all people or the whole world in general, its specifically about Israel.
Zechariah 12:12-13
The land shall mourn, each tribe by itself: the family of the house of David by itself, and their wives by themselves; the family of the house of Nathan by itself, and their wives by themselves; the family of the house of Levi by itself, and their wives by themselves; the family of the Shimeites by itself, and their wives by themselves; and all the families that are left, each by itself, and their wives by themselves.
Jesus quotes from zechariah 12:12 as occuring shortly after the destruction of 1st century jerusalem.
Matthwe 24:29-30
Immediately after the tribulation of those days the sun will be darkened, and the moon will not give its light, and the stars will fall from heaven, and the powers of the heavens will be shaken. Then will appear in heaven the sign of the Son of Man,
and then all the tribes of the earth will mourn, and they will see the Son of Man coming on the clouds of heaven with power and great glory.
Jerusalem is destroyed because they did not recognize the time of Jesus' coming......
Luke 19:43-44 For the days will come upon you, when your enemies will set up a barricade around you and surround you and hem you in on every side and tear you down to the ground, you and your children within you. And they will not leave one stone upon another in you,
because you did not know the time of your visitation.”
.......Which correlates with the Vineyard owner "COMING" to destroy the wicked tenants for killing his son.
Matthew 21:40-45
When therefore the owner of the vineyard comes, what will he do to those tenants?” They said to him, “He will put those wretches to a miserable death and let out the vineyard to other tenants who will give him the fruits in their seasons.” Jesus said to them, “Have you never read in the Scriptures: “‘The stone that the builders rejected has become the cornerstone;
d
this was the Lord’s doing, and it is marvelous in our eyes’? Therefore I tell you, the kingdom of God will be taken away from you and given to a people producing its fruits. And the one who falls on this stone will be broken to pieces; and when it falls on anyone, it will crush him.”
e When the chief priests and the Pharisees heard his parables,
they perceived that he was speaking about them.
Thus, I'm not sure on what grounds we can separate the coming of the vineyard owner to destroy the wicked tenants in association with kill His son and their mourning because of this?