“Then he replied to me, “This is this message from the LORD to Zerubbabel: ‘Not by might nor by power, but only by My Spirit,’ says the LORD of the Heavenly Armies.” (Zechariah 4:6)

I believe that one of the implication of this is the ‘Universal Reconciliation of all creation to Him’ by “His Spirit” simply because (note the word “SAVED” in the verse below):

Every Creature will declare that “Jesus is Lord” (swearing an allegiance to Him):

“Turn to Me and be SAVED, all who live at the ends of the earth, because I am God, and there is no other. I have bound Myself with an oath. A Word has gone out from My righteous Mouth that will not be recalled, “Every knee will bow to Me and every tongue will swear [allegiance].” (Isaiah 45:22 – 23)

We know the verse above refers to ‘Jesus’ (God manifested in Flesh) because:

“and every tongue acknowledge that Jesus Christ is Lord, to the glory of God the Father.” (Philippians 2:11)

And this is ‘only’ possible by “His Holy Spirit” (note, ‘by His Holy Spirit’):

“Therefore I want you to know that no one who is speaking by the Spirit of God says, “Jesus be cursed,” and no one can say, “Jesus is Lord,” except by the Holy Spirit.” (1 Corinthians 12:3)

Can you see it?
That’s how by “His Spirit” or “His Holy Spirit” alone (‘not’ by might, ‘nor’ by power) He Will accomplish it.

P/S:

Since God has bound Himself with an Oath to do it, the Salvation of all is predestined too in time when ‘every tongue’ (rational creature) swears allegiance to Him —> Absolute Assurance.

Glory be to Him for His Gracious Salvation!

Therefore, bury your swords and come Home to Him:

“He (God) will judge between the nations and will settle disputes for many peoples. They will beat their swords into plowshares and their spears into pruning hooks. Nation will not take up sword against nation, nor will they train for war anymore.” (Isaiah 2:4)

Even this prophet testifies the “same” outcome too:

“And He will judge between many peoples And render decisions for mighty, distant nations. Then they will hammer their swords into plowshares And their spears into pruning hooks; Nation will not lift up sword against nation, And never again will they train for war.” (Micah 4:3)