Jamieson, Fausset and Brown on Zechariah 2:12

12. Judah his portion in the holy land--Lest the joining of the Gentile "nations to Jehovah" (Zec 2:11) should lead the Jews to fear that their peculiar relation to Him (De 4:20; 9:29; 32:9) as "His inheritance" should cease, this verse is added to assure them of His making them so hereafter "again."

choose Jerusalem again--The course of God's grace was interrupted for a time, but His covenant was not set aside (Ro 11:28, 29); the election was once for all, and therefore shall hold good for ever.