Adam Clarke on Zechariah 6:13

Even he shall build the temple - Joshua, not Zerubbabel.

He shall bear the glory - Have all the honor of it; for none can do this but himself. The Messiah is still intended.

And shall sit and rule upon his throne - For the government of the Church shall be upon his shoulder.

And he shall be a priest upon his throne - He shall, as the great high priest, offer the only available offering and atonement; and so he shall be both king and priest, a royal king and a royal priest; for even the priest is here stated to sit upon his throne.

And the counsel of peace shall be between them both - Whom? Zerubbabel and Joshua? Certainly not Zerubbabel, for he is not mentioned in all this prediction; but, as the Messiah is intended, the counsel of peace - the purpose to establish peace between heaven and earth, must be between the Father and the Son.