IMPORTANT: For an option to resolve YES the winner of a major needs to use that character during Grand Finals, Winner's Finals, Winner's Semifinals, Loser's Finals, Loser's Semifinals, or Loser's Quarterfinals. Also, they must win at least one of the games in which they used that character.
In addition to the rules above, Zelda only counts if at least three of the enemy's stocks are taken entirely by Zelda without transforming into Sheik. So the enemy must go from 0% to death without Sheik's involvement, three times, in a single game.
I will be deferring to Liquipedia on which tournaments count as a 'Major'.
Be sure to check out the SSBM Tournament dashboard! 🏆
How exactly does Zelda resolve? What if a Sheik player accidentally transforms into Zelda and lands a single "get-off-me" b-air before transforming back? What if the Sheik player transforms into Zelda solely for the purpose of recovering and then wins the game? What if the transformation + recovery is plausibly non-determinative (e.g. it was done in a 4-to-1-stock situation and the Sheik player almost certainly would have won anyway)?
@NBAP Woops I thought of that case but didn't actually type what I thought of 😝 I'll add it to description now