To be fair, as much as I like the idea of Skull Kid in Smash (Majora's Mask is love), Zelda is 100% perfectly represented as it is.
It's really not though, there's a total of 3 characters, one done very poorly, one repeated twice, and an alternate form one took in one of the games.
If you mean to say that the tri-force trio represent Zelda in its entirety then I have to hard disagree there. The Zelda world resets (almost) every single game. Unique mechanics of the majority of the series aren't even present, and neither are most of the very memorable characters that fill these incredible worlds.
People treat Zelda like it's Mario, a recurring cast rehashing the same game but with unique improvements and elements to each game. It's not, Zelda is like Fire Emblem, resetting its cast every game except for a small few characters. Yes those characters who return should be represented, but that doesn't mean that it's completely represented with just them.