Jamieson, Fausset and Brown on Zechariah 9:11

11. As for thee also--that is, the daughter of Zion," or "Jerusalem" (Zec 9:9): the theocracy. The "thee also," in contradistinction to Messiah spoken of in Zec 9:10, implies that besides cutting off the battle-bow and extending Messiah's "dominion to the ends of the earth," God would also deliver for her her exiled people from their foreign captivity.

by the blood of thy covenant--that is, according to the covenant vouchsafed to thee on Sinai, and ratified by the blood of sacrifices (Ex 24:8; He 9:18-20).

pit wherein ... no water--Dungeons were often pits without water, miry at the bottom, such as Jeremiah sank in when confined (Ge 37:24; Jr 38:6). An image of the misery of the Jewish exiles in Egypt, Greece, &c., under the successors of Alexander, especially under Antiochus Epiphanes, who robbed and profaned the temple, slew thousands, and enslaved more. God delivered them by the Maccabees. A type of the future deliverance from their last great persecutor hereafter (Is 51:14; 60:1).