Some of the people of Israel have returned home from their captivity in Babylon and are now faced with a monumental task of rebuilding the temple. When opposition set in the work stopped and many of them just moved on to focus on their own lives. It was a discouraged and despondent group. But they were missing out on the blessings of God because of their apathy. So here in the beginning of Zechariah we hear God calling out to return to Him. It's one of the greatest invitations in Scripture. We are invited to turn ourselves to a holy God. And as we do, we will find Him and be blessed.
The book of Zechariah is meant to bring encouragement to the people as they see that God is still for them and is doing a work among them.