As you can see in this replay, the pathetic and weak Kyurem-Black goes up against the two strongest Fairy types in AG, Cleffa and Igglybuff. during the battle, Kyurem stupidly decides to use Devastating Drake against Igglybuff, which results in a failure due to Fairy types resisting Dragon moves. Then, not thinking straight due to being in a state of fear, Oranguru uses Instruct on Kyurem, which failed. Cleffa and Igglybuff, with the opportunity to do so, OHKOed the opposing Kyurem and Oranguru with their signature moves, Splash and Work Up. That's probably how the battle went, I think.
TL;DR: Instruct doesn't work on z-moves