Ezekiel was commanded to watch the man in heaven measure a future temple because there was no existing temple on earth.
However, John was told to personally measure the existing temple on earth.
Zechariah 14 -- Zechariah's OT prophecy about a New Jerusalem was fulfilled and it is the NT Church.
Hebrews 12:22-24
But you have come to Mount Zion, to the city of the living God, the heavenly Jerusalem. You have come to thousands upon thousands of angels in joyful assembly, 23 to the church of the firstborn, whose names are written in heaven. You have come to God, the Judge of all, to the spirits of the righteous made perfect, 24 to Jesus the mediator of a new covenant, and to the sprinkled blood that speaks a better word than the blood of Abel. niv
The New Jerusalem on earth is the Church which came into existence at Pentecost 2000 years ago when the Apostles were empowered to carry out Jesus' command to build His Church.
All people who are saved by the blood of Jesus Christ become new temples of God.
Any new temple built in Jerusalem for inferior animal sacrifices would be a denial of Jesus Christ's perfect sacrifice. This would be a terrible insult to God.
1 Corinthians 3:16-17
Do you not know that you are the temple of God and that the Spirit of God dwells in you? 17 If anyone defiles the temple of God, God will destroy him. For the temple of God is holy, which temple you are. nkjv
The spiritual enemies of God and His Church are all the people living today who do not believe that Jesus is God and Savior.
In Zechariah 14, we see God dealing directly against the nations/peoples who are against God's people who are the Jews.
In Revelation 19 we see God dealing directly against the nations/peoples who are against God's people/His Church, the followers of Jesus Christ.
There is no distinction between nationalities such as Jew or Gentile in the New Covenant. Either a person is a Christian or else he is not a Christian. A Jewish Christian is one of the people of God. A Gentile Christian is one of the people of God.
Galatians 3:28
There is neither Jew nor Gentile, neither slave nor free, nor is there male and female, for you are all one in Christ Jesus. niv
1 Peter 2:9-10
But you are a chosen people, a royal priesthood, a holy nation, God’s special possession, that you may declare the praises of him who called you out of darkness into his wonderful light. 10 Once you were not a people, but now you are the people of God; once you had not received mercy, but now you have received mercy. niv