This passage is commented upon in section 5-30 . Section 5-4-2 considers it too in terms of its connection with the Satan in the Heavenly court which we meet in Job 1. According to Dt. 32:8,9 LXX, humanity has been divided up "according to the number of the angels of God"; each nation has its Angelic representative in Heaven. These Angels are spoken of as being 'punished' in the sense that their charges on earth are punished. Note the parallelism in Is. 24:21,22:
"Yahweh will punish
The host of heaven in heaven
And on earth the kings of the earth".
This doesn't mean that the representative Angels are themselves sinners; but they are identified in the court of Heaven with those on earth whom they represent.
Zechariah 3 was written in the context of the Jews in Babylon. It has been shown that the Babylonians believed that each person has a god who accuses them (1). As elsewhere, Zechariah and the prophets allude to contemporary beliefs and deconstruct them, i.e. they show the truth about these matters as Yahweh wished His people to understand them, just as Moses alluded to creation myths in order to show what was false and to explain the truth about some of the matters they touched upon. So here Zechariah is making the point that the truth is that in the court of Heaven, Angels represent human beings and organizations and their positions and accusations against God's people; and it is God who judges those accusations, and sends forth His Angels to implement His subsequent judgment of the cases upon earth. Paul may have this in mind when he exults that if God and Christ are on our side, we now have no accusers- for they are the only ones who can bring valid accusation against us. And even if we have accusers, the fact that they are our justifiers means that effectively, no such accusation is of any power (Rom. 8:33,34).
(1) Rivkah Scharf Kluger, Satan In The Old Testament (Evanston: Northwestern University Press, 1967), pp. 134,135.