Adam Clarke on Zechariah 6:12

Behold the man whose name is The Branch! - I cannot think that Zerubbabel is here intended; indeed, he is not so much as mentioned in Zac 3:8. Joshua and his companions are called אנשי מופת anshey mopheth, figurative or typical men; the crowning therefore of Joshua in this place, and calling him the Branch, was most probably in reference to that glorious person, the Messiah, of whom he was the type or figure. The Chaldee has, "whose name is my Messiah," or Christ.

And he shall grow up out of his place - That is, out of David's root, tribe, and family.

And he shall build the temple of the Lord - This cannot refer to the building of the temple then in hand, for Zerubbabel was its builder: but to that temple, the Christian Church, that was typified by it; for Zerubbabel is not named here, and only Joshua or Jesus (the name is the same) is the person who is to be crowned and to build this spiritual temple.