Z-Partner

"Z-Partner" is a term coined by Boulder the Lycanroc in The Legend of Fox the Brave, first used in the Prologue of the story Storm of Darkness. It is a term used to describe a human or Mobian that helps a Pokemon use a Z-Move.

The Player(Pokemon Sun and Moon)
Pokemon:
 * Any Pokemon on their Team

The Player(Pokemon Ultra Sun and Ultra Moon)
Pokemon:
 * Any Pokemon on their Team

Austin Smith
Pokemon:
 * Boulder the Lycanroc

Lerry the Bear
Pokemon:
 * Storm the Buizel(demonstration)

Shamar the Fennec
Pokemon:
 * Finnick the Lycanroc(demonstration)

Boulder the Lycanroc
Known Moves:
 * Continental Crush
 * Used When?: Return of Evil, the chapters Continental Crash(failed), Mastering Moves(succeeded), and Crushing Victory(succeeded); Shadows of Vengeance, the chapters Crushing a Shadow and Battle of Darkness(boosted by Chaos Control); Storm of Darkness, the chapter The Attack(failed)
 * With Who?: Austin Smith
 * Original Move: Unknown, likely Stone Edge

Finnick the Lycanroc
Known Moves:
 * Continental Crush
 * Used When?: Return of Evil, the chapter Continental Crash(demonstration)
 * With Who?: Shamar the Fennec
 * Original Move: Stone Edge

Storm the Buizel
Known Moves:
 * Hydro Vortex
 * Used When?: Return of Evil, the chapter Continental Crash(in training)
 * With Who?: Lerry the Bear
 * Original Move: Unknown, either Aqua Jet or Water Gun

Trivia
Z-Partner is not an official term used in the Pokémon franchise, it is a term coined for The Legend of Fox the Brave.