Matthew's Donkey and Colt fulfillment citation hides an unfulfilled Messianic prophecy in Zechariah 9:10. Mathew quotes Zechariah 9:9 but forgets the next verse (which begins with “and”, i.e. it is a continuation). I.E. the sign isn't what happens in Zechariah 9:9, but what happens in 9:10. Jesus did not fulfill this prophecy because he died before he brought about world peace (etc).