Zechariah 14:20 says "HOLY TO THE LORD" will be inscribed on what?

Answer: The bells of the horses

On that day the bells of the horses will bear "HOLY TO THE LORD" (KJV: "HOLINESS UNTO THE LORD"), and the pots in the LORD's house will be like sprinkling bowls.

“On that day, HOLY TO THE LORD will be inscribed on the bells of the horses, and the cooking pots in the house of the LORD will be like the sprinkling bowls before the altar.”— Zechariah 14:20 (BSB)