Regarding Jesus existing before the world was created, that we do not dispute for even the devil and his angels existed before man was ever created upon the face of the earth. Jesus was and we also believe that he is the Word that visited the prophets in the Old Testament and delivered messages. In this same manner, Satan also approaches members of his own synagogue and gives them messages concerning how his global 666 plan will be imposed on the inhabitants of the world.
We do believe Jesus is the arch angel Michael because of two principal verses in the Bible
- Daniel 12:1
At that time Michael, the great prince who protects your people, will arise. There will be a time of distress such as has not happened from the beginning of nations until then. But at that time your people—everyone whose name is found written in the book—will be delivered.
Michael your prince, Jesus is the Prince of Peace. Is this an end time prophecy concerning the raising of the dead and their judgment? What's an arch angel doing in the middle of it? We do know it's Jesus who is central to the end of the age because his return triggers it.
- Revelation 12:7
Now war arose in heaven, Michael and his angels fighting against the dragon. And the dragon and his angels fought back,
It reaches a point where the devil has to be prevented from accessing heaven and force needs to be used so war arises in heaven, Jesus who is at the right hand of God commands his angels to fight just as he told us while he was here on earth that he can ask of his Father legions of angels and they would come to his defense, I want you to pause and think of all the instances of scripture that say God would send angels to the defense of Jesus, remember the temptation at the pinnacle of the temple?
Don't you realize that I could ask my heavenly Father for angels to come at any time to deliver me? And instantly he would answer me by sending more than twelve legions of angels to come and protect us.
For it is written: “’He will command his angels concerning you to guard you carefully;
Scripture shows that there is divine command that has been given to Jesus over the angels and he is the One leading them to war against the devil and his angels in Revelation.
The verse in Zechariah you posted could also be an end time prophecy that proclaims that the inhabitants of the world shall see Jesus in the glory of his Father in the skies and they shall mourn
Mathew 24:30
“Then will appear the sign of the Son of Man in heaven. And then all the peoples of the earth will mourn when they see the Son of Man coming on the clouds .
That is because scripture doesn't say that anyone mourned during the crucifixion but it does confirm that after the world sees him in the sky then they shall mourn.
To wind up, how does Jesus shout with the voice of the arch angel if he is not the arch angel?
1 Thessalonians 4:16
“For the Lord himself will come down from heaven with a shout of command, with the voice of the archangel and with the trumpet of God, and the dead in Christ will rise first”