It is not known to evolve into or from any other Pokémon.
Zephy currently has not been officially released.
'A mysterious Pokemon that appears to be a cross between PLUSLE and ARTICUNO. In legends, it visited artists and gave them ideas for their next masterpiece
Physically, Zephy heavily resembles both Articuno and Plusle. Zephy is a bipedal rabbit-like Pokémon with a cream-colored head, upper torso and belly, and icy blue legs with bluish gray talons for feet. It has red ears, red cheeks and paws, and unlike Plusle, large blue eyes. It also has a small black nose, and fluffy white fur on the top of its head and around its neck. It has a blue ribbon-like tail, and blue wings with white centers that sprout from its lower back. Zephy is a female-only Pokémon with no male counterpart.
A mysterious Pokémon that appears to be a cross between Articuno and Plusle, Zephy is often told of in legends, where it gave many artists ideas for their next masterpiece.
Zephy's design concept dates back to Twitch's middle school years. (1) (2).
The only other Pokémon that has the same type combination as Zephy is Frost Rotom.
The Generation VIII Pokémon Arctozolt also shares the Electric-Ice typing, though Arctozolt was released after Uranium. Coincidentally, both are fusions between an Electric-type and an Ice-type, though Zephy seems to be naturally fused while Arctozolt was fused using science.
Twitch uses Zephy as her personal icon.
The fact that Hidden Power (move) is in Zephy's current moveset is possibly a reference to Zephyr, a Plusle with an Ice Type Hidden Power, owned by Twitch (3). Zephy's first incarnation (and by extension Zephy) may possibly borrow their concept and type from this Plusle.
Zephyr is based on an old design by Twitch, one of the developers of the game. Appearance-wise, it is inspired by both Articuno and Plusle. (4)
Zephy is a corruption of Zephyr, which was the name Twitch gave to its original incarnation (5) The defintion of zephyr is "a light breeze or the west wind".