What does Zechariah 14:12 mean?

Here’s what the Lord will do to all the nations that attacked Jerusalem: their flesh will rot while they’re still standing, their eyes will rot in their sockets, and their tongues will rot in their mouths. Zechariah 14:12 - Modern Text Bible

(God will strike Jerusalem’s enemies with a terrifying plague, showing his power to protect his people and judge their attackers.)