supernatural strength

It would be years before the prophecies about the Messiah would come true.  Jerusalem was being rebuilt. God through His Spirit moved upon the heart of the prophet and hope grew.  His purposes would be accomplished.  Human effort would be joined by God's might and strength.  He didn't know all the details but he knew who was in charge.  Zechariah declared under the inspiration of the Holy Spirit that God was up to something. He quotes the word of the angel in his vision:
6 Then he said to me, “This is the word of the LORD to Zerubbabel: Not by might, nor by power, but by my Spirit, says the LORD of hosts.
We can trust that God can get His purposes accomplished.  Let's join the adventure!  Praise God!