What does Zechariah 14:5 mean?

You’ll run out through the valley between the mountains, because the valley will stretch all the way to Azal. You’ll run just like people did when the earthquake hit during King Uzziah’s time. Then the Lord my God will come, and all his holy ones will be with him. Zechariah 14:5 - Modern Text Bible

(This verse describes people fleeing for safety as God arrives with his holy ones, echoing a past earthquake to show the fear and urgency.)