Zechariah 4: strength to rebuild the temple

Zechariah has another vision concerning the temple:

6 Then he said to me, “This is the word of the Lord to Zerubbabel, saying, ‘Not by might nor by power, but by My Spirit,’ says the Lord of armies. 7 ‘What are you, you great mountain? Before Zerubbabel you will become a plain; and he will bring out the top stone with shouts of “Grace, grace to it!”’”

The great mountain must be great obstacles to rebuild the temple. These obstacles will be removed by the Spirit of the Lord.
I pray that my father trust in the Lord before he dies, but he is demented and can't reason well. I must believe that by the Spirit, the Lord can remove obstacles.