From Bulbapedia, the community-driven Pokémon encyclopedia.
Zachary (Japanese: ゼカー Zeker) is a recurring character in the Pokémon anime who appeared in Who's Flying Now? and A Sky High Gym Battle!.
He lives in Fortree City and is employed as the Gym assistant at the Fortree Gym. Among his responsibilities are refereeing Gym battles between Winona and her opponents, as well as maintaining and watching the Gym while she is away.
When Ash and his friends arrived at the Fortree Gym, Zachary was there to greet them. He informed them that Winona was at the Feather Carnival and could not battle at that moment.
Zachary refereed the match between Ash and Winona in the following episode.