What does Zechariah 9:5 mean?

Ashkelon will see this and be terrified. Gaza will writhe in pain, and so will Ekron, because their hope is gone. Gaza will lose its king, and Ashkelon will be deserted. Zechariah 9:5 - Modern Text Bible

(The downfall of Tyre will frighten other Philistine cities, who will also face disaster.)