Acts shows us the fulfillment of the promise in Zechariah 4: "Not by might, nor by power, but by My Spirit, says the Lord of hosts." (verse 6)
You will receive power when the Holy Spirit has come on you, and you will be My witnesses in Jerusalem, in all Judea and Samaria, and to the ends of the earth. (Acts 1:8)
When the day of Pentecost had arrived, they were all together in one place. 2 Suddenly a sound like that of a violent rushing wind came from heaven, and it filled the whole house where they were staying. And tongues, like flames of fire that were divided, appeared to them and rested on each one of them. Then they were all filled with the Holy Spirit and began to speak in different languages, as the Spirit gave them ability for speech. (Acts 2:1-4)
And it will be in the last days, says God,
that I will pour out My Spirit on all humanity;
then your sons and your daughters will prophesy,
your young men will see visions,
and your old men will dream dreams.
I will even pour out My Spirit
on My male and female slaves in those days,
and they will prophesy. (Acts 2:17-18)
Hebrews chapter 9 and 10 show us the Priest King. I think these verses in the NLT sum it up:
For Christ did not enter into a holy place made with human hands, which was only a copy of the true one in heaven. He entered into heaven itself to appear now before God on our behalf. And he did not enter heaven to offer himself again and again, like the high priest here on earth who enters the Most Holy Place year after year with the blood of an animal. If that had been necessary, Christ would have had to die again and again, ever since the world began. But now, once for all time, he has appeared at the end of the age to remove sin by his own death as a sacrifice.
And just as each person is destined to die once and after that comes judgment, so also Christ died once for all time as a sacrifice to take away the sins of many people. He will come again, not to deal with our sins, but to bring salvation to all who are eagerly waiting for him. (Hebrews 9:24-27)
But our High Priest offered himself to God as a single sacrifice for sins, good for all time. Then he sat down in the place of honor at God’s right hand. There he waits until his enemies are humbled and made a footstool under his feet. For by that one offering he forever made perfect those who are being made holy.
And the Holy Spirit also testifies that this is so. For he says,
“This is the new covenant I will make
with my people on that day, says the Lord:
I will put my laws in their hearts,
and I will write them on their minds.”
Then he says,
“I will never again remember
their sins and lawless deeds.”
18 And when sins have been forgiven, there is no need to offer any more sacrifices.
There are lots of complicated prophecies in Zechariah. But there are also lots of simple foundational spiritual truths. God loves His people. God will remove our sin when we place our faith in Him. God has a glorious plan for the future.