Zechariah 10:6 promises to "strengthen the house of Judah, and save the house of Joseph." Since the days of Jeroboam, Israel had been a divided nation. The prophets consistently looked forward to a day when the "two sticks" would become one in God's hand.
This was not a promise for a future Zionist state, but for the New Covenant Church. In Christ, the dividing wall was torn down (Ephesians 2:14-15). The Gospel gathered the "lost sheep of the house of Israel" (Ephraim/Joseph) along with Judah, creating "one new man." The reunification of Israel is the spiritual unity of the body of Christ, where there is no longer a division between tribes or nations.