I'm quite disappointed in its Signature move. Now there isn't any hidden attack to link to Zygarde to give him in a possible third. Doesn't look like there is much they can add to him to make him impressive enough for focus.
It's because alot of people try to spec Zygarde like any other dragon (i.e. outrage, dragon pulse, earthquake, etc) basically a garchomp in disguise... instead Zygarde needs to be made into a WALL. he is the onyl dragon capible of Walling besides Giratina. but unlike Giratina, Zygarde has access to Camoflauge.. use it and instantly Zygarde loses all it's vulnerabilities to ice, fairy, and dragon so it is a more efficient wall, as fighting moves hardly leave a scratch on it as compared to fairy/ice/dragon moves..
This is my favorite set up, i've used it sucessfully and even have videos showing it can be done sucessfully and totally sweep your opponent..
Prior to Pokemon Bank's release, before I had access to my Arceus, I used an Adamant Zygarde as a Pseudo-Arceus.. 252 EVs in HP, 252 in Attack. Have him hold a Silk Scarf.. Send him out to someone who can't really hurt him, move 1. Use Camoflauge.. move 2. use Coil or Dragon Dance (optional).. move 3. Extreme speed the crap out of your opponents.. you'll one-shot everything that isn't resistant to normal like Arceus does. Zygarde's Attack is near the god Pokemon itself... @level 50 Adamant Arceus' attack is 227, Adamant Zygarde's attack is 215...
So with the use of camoflauge, Zygarde turns into a normal type, so it gets STAB on Extreme Speed, and mixed with the Silk Scarf boost, and a Coil or Dragon Dance Boost (optional), nothing will survive..