Here, look at this picture. We DON'T really see any curves. It appears that Zelda is flat-chested in this picture. Because of the location of the neck (and the fact that it blends in), the jewelry and dress look lower than they are, and, in an attempt to not sound like a preverted polygon-passionate pig, where her dress begins, based on the normal appearance of female anatomy, is where her (feeling uncomfortable saying this) boobs would end. But, since she's leaning forward, I can see it's an optical illusion by itself, and the shading makes it prominent.
Now we see the fan-service chest.