These two sentences mean the same thing and intensify the command to rejoice. Yahweh is speaking to the people of Jerusalem as if they were present, but they were not there. (See: [[rc://en/ta/man/translate/figs-parallelism]] and [[rc://en/ta/man/translate/figs-apostrophe]])
"Zion" is the same as "Jerusalem." The prophet speaks of the city as if it is a daughter. See how you translated "daughter of Zion" in [Zechariah 2:10](../02/10.md).
This alerts the reader to pay special attention to the surprising statement that follows. Alternate translation: "Pay attention!" or "Here is a surprising fact!"
These two phrases mean basically the same thing and refer to one animal. The second phrase clarifies that this is a young donkey. Alternate translation: "on a young donkey" (See: [[rc://en/ta/man/translate/figs-doublet]])