He reigns NOW. His kingdom is not of this world and is not seen with the eye and the Zion He rules from cannot be touched with the hand.
Isa 9:6 For unto us a child is born, unto us a son is given: and the government shall be upon his shoulder: and his name shall be called Wonderful, Counsellor, The mighty God, The everlasting Father, The Prince of Peace.
Isa 9:7 Of the increase of his government and peace there shall be no end, upon the throne of David, and upon his kingdom, to order it, and to establish it with judgment and with justice from henceforth even for ever. The zeal of the LORD of hosts will perform this.
Only a deluded person would think these prophesies (the ones bolded) have already taken place; have already been fulfilled.
We may call Christ the "Prince of peace," but the world is not at peace. There is no peace in this world.
The government is not upon his shoulder.
Of the increase of his government there shall be no end. Not happening.
He shall be upon the throne of David. Not happening.
He shall establish (his throne) with judgment and justice forevermore. Not happening.
--None of these have happened or are happening.
So that you might understand the verse, look in another translation:
(ISV) Of the growth of his government and peace there will be no end. He will rule over his kingdom, sitting on the throne of David, to establish it and to uphold it with justice and righteousness from this time onward and forevermore. The zeal of the LORD of the Heavenly Armies will accomplish this.
--It infers a kingdom on earth, not in heaven.
Look elsewhere:
Zec 14:2 For I will gather all nations against Jerusalem to battle; and the city shall be taken, and the houses rifled, and the women ravished; and half of the city shall go forth into captivity, and the residue of the people shall not be cut off from the city.
--This battle has not happened yet, but it looks like it could any time now.
Zec 14:3 Then shall the LORD go forth, and fight against those nations, as when he fought in the day of battle.
Zec 14:4 And his feet shall stand in that day upon the mount of Olives, which is before Jerusalem on the east, and the mount of Olives shall cleave in the midst thereof toward the east and toward the west, and there shall be a very great valley; and half of the mountain shall remove toward the north, and half of it toward the south.
--The Lord has not come yet, but verse 3 says he will.
And in verse 4 it says he will come to the mount of Olives and the mount shall be divided. IOW, a great earthquake shall take place. This has not happened yet.
Zec 6:12 And speak unto him, saying, Thus speaketh the LORD of hosts, saying, Behold the man whose name is The BRANCH; and he shall grow up out of his place, and he shall build the temple of the LORD:
--The Lord, known here as The Branch, when he comes will build a temple for himself.
Zec 6:13 Even he shall build the temple of the LORD; and he shall bear the glory, and shall sit and rule upon his throne; and he shall be a priest upon his throne: and the counsel of peace shall be between them both.
--It will be built on this earth, and he shall sit and rule from a throne that will be built in this temple.
Zec 6:15 And they that are far off shall come and build in the temple of the LORD, and ye shall know that the LORD of hosts hath sent me unto you. And this shall come to pass, if ye will diligently obey the voice of the LORD your God.
--All the world will know that Christ is Lord in that day.
Does all the world know that Christ is Lord today? Obviously not!
What shall it be like when Christ comes and sets up his Millennial Kingdom.
He will remove the curse, and it will return as it was in the garden of Eden.
Isa 11:6 The wolf also shall dwell with the lamb, and the leopard shall lie down with the kid; and the calf and the young lion and the fatling together; and a little child shall lead them.
Isa 11:7 And the cow and the bear shall feed; their young ones shall lie down together: and the lion shall eat straw like the ox.
Isa 11:8 And the sucking child shall play on the hole of the asp, and the weaned child shall put his hand on the cockatrice' den.
Isa 11:9 They shall not hurt nor destroy in all my holy mountain: for the earth shall be full of the knowledge of the LORD, as the waters cover the sea.
Isa 11:10 And in that day there shall be a root of Jesse, which shall stand for an ensign of the people; to it shall the Gentiles seek: and his rest shall be glorious.
Is it like that now?