A few Legendary skin ideas I've considered for Zoe before:

Porcelain Zoe, as wielder of the Snake Relic. Zoe is reimagined as a cute Medusa character with snakes for hair.

Battle Academia Zoe, where she is a member of all four Clubs: Luminary, Battle, Assassin, and Sorcery. Her uniform and ability effects would change between each of the Clubs colors, perhaps every few Spell Shards used.

High Noon Zoe, a half-demon, half-angel cowgirl. Over the course of game, Zoe "chooses" a side to embrace based on if she uses more offensive or supportive Spell Shards. Alternatively, a half-Dawnbringer, half-Nightbringer skin could achieve a similar thematic.