Chapters 9-14 are part 2 of the book of Zechariah. The time Zechariah received the burdens of these chapters is not defined as it was in the first 8 chapters. The burdens Zechariah has in the first 8 verses are against cities along the Mediterranean coast who are long time adversaries against Israel. The judgments predicted may have been fullfilled when Alexander the Great marched through these cities enroute to Egypt. When he then turned to Persia, he spared Jerusalem along the way (v8) by God's protecting mercy to His people.
In contrast to the proud peoples and proud king Alexander, the prophet Zechariah sees the King of Israel coming to his people, exactly as He did in Matthew 21:5 and John 12:15. He is just and lowly and riding on a donkey. The rest of this message focuses on the humility of our Lord Jesus, exalting the King of Kings and Lord of Lords.