I find this really interesting. Zelda is not very good in Singles, but in brawl she was pretty decent in doubles. That might hold true in smash 4 and she could be a good partner for Ness.
The multiple Din's Blaze setups would not be extremely difficult to setup in a 2v1 situation, or if you are able to knock both opponents offstage in the same direction.
What I like a lot about Zelda and Ness as a team is that you can let Ness play the primary aggressor and let Zelda play support. Have Ness on the frontline fighting kind of 2v1 and have Zelda punishing them when they hit Ness. And you can send Din's into the 3 of them and not worry about Ness cause he can heal it. Seems like a decent team really.