The Messiah will:
Come from the offspring of the woman, therefore, will be fully human,
Will crush the head of the serpent (Satan), therefore, will defeat sin and death.
The serpent will attack his heel, therefore, he will suffer and perhaps even die.
And I will put hostility between you and the woman and between your offspring and her offspring; her offspring will attack your head, and you will attack her offspring’s heel.
The following is adapted from Matthew Henry's Commentary:
This gracious revelation of a Saviour came unasked, and unlooked for. Without a revelation of mercy, giving some hope of forgiveness, the convinced sinner would sink into despair, and be hardened. By faith in this promise, our first parents, and the patriarchs before the flood, were justified and saved. Notice is given concerning Christ:
His incarnation, or coming in the flesh. It speaks great encouragement to sinners, that their Saviour is the Seed of the woman, bone of our bone, Hebrews 2:11,14.
His sufferings and death; pointed at in Satan's bruising his heel, that is, his human nature. And Christ's sufferings are continued in the sufferings of the saints for his name. The devil tempts them, persecutes and slays them; and so bruises the heel of Christ, who is afflicted in their afflictions. But while the heel is bruised on earth, the Head is in heaven.
His victory over Satan thereby. Christ baffled Satan's temptations, rescued souls out of his hands. By his death he gave a fatal blow to the devil's kingdom, a wound to the head of this serpent that cannot be healed. As the gospel gains ground, Satan falls.
Listen now, Joshua the high priest, both you and your colleagues who are sitting before you, all of you are a symbol that I am about to introduce my servant, the Branch. See, the stone I have set in front of Joshua! There are seven eyes on that one stone, and I will engrave an inscription on it,’ says the Lord Almighty, ‘and I will remove the sin of this land in a single day'.
The Geneva Study Bible writes on Zech 3:8:
That is, Christ, who did so humble himself, that he not only became the servant of God, but also the servant of men: and therefore in him they should have comfort, even though in the world they are condemned