Z-Ring appears in 4 version groups since Generation VII, a Gameplay item in the Key Items pocket
PokéAPI item 838 of 2,223, Gameplay category, Key Items pocket
Effect, in PokéAPI's words
Z-Ring: “Allows the player’s Pokémon to use Z-moves.”
Games
Z-Ring is listed in the text of 4 version groups, first in Generation VII
Game index by generation
IIIIIIIVVVIVIIVIIIIX
Named in
Sun and MoonUltra Sun and Ultra MoonLet's Go Pikachu and Let's Go EeveeSword and Shield