Is Zygarde just worthless?
No way, Zygarde is a tank.. Zygarde use to be a staple on my team, if EV trained right, it can tank a direct moonblast from a modest Xerneas or a draco meteor, then proceed to dish out a hard hitting Outrage or Earthquake/Stone Edge. Also he's a good game sweeper, capable of taking out opponents in the red or yellow with extreme speed.
Another option to make Zygarde into a killing machine that can rival god itself, Arceus.. EV Spec Zygarde for max attack and max HP, and have it's moves be Camouflage, Extreme Speed, Shadow Claw, and Swords Dance while holding the silk scarf.
The idea is to switch Zygarde out into an electric Pokemon or any Pokemon who can't really phase Zygarde and likely switch out as the opposing trainer would expect you to one-shot their Pokemon with earthquake/stone edge/dragon pulse, instead you use Camouflage which will turn his type from Dragon/Ground into Normal, thus eliminating his vulnerabilities to Fairy, Ice, and Dragon (probably their switch-in), this alone can cause confusion to your opponent who don't know what camouflage is, as evident as they try to still zygarde with the now-weaker ice/fairy/dragon moves, even if their Pokemon may know a fighting move or are even a fighting type but most likely they won't ever have the chance to lay a single attack on regarded because now much like Arceus, you now get STAB on Extreme Speed and the 20% boost thanks to the Silk Scark means that Extreme Speed's Base power is now elevated to a whopping 144 power! Mix that with a max Attack EV and Zygarde's Base Attack and hopefully perfect attack IV, it is capible of one-shotting lesser defensive Pokemon or devastating the health of bulky/wall Pokemon such as Blissey.
Then if it's safe to do so, a Swords Dance will dramatically increase Zygarde's one-shot potential on Bulky Walls and ineffective normal resisting Pokemon.
And with Extreme Speed being a +2 Priority move, you'll easily outspeed your opponents, including priority HA Pokemon such as Talonflame w/Galewings or Prankster pokemon and most likely one-shotting them before they get to attack or use a status move, and even if they did survive (most likely in yellow/red), with Zygarde's Physical Bulk and max HP EVs, it'll most likely shrug off the minute damage and proceed to destroy them next turn.
So in other words, Zygarde is the Poor-Man's version of Arceus... if Arceus was not at your disposal. Thanks to his bulkiness, he is capable of surviving a direct modest Mewtwo aura blast where your average Arceus would probably die..
Plus the confusion factor that camouflage causes to opponents that I have personally experienced is just icing on the cake. Expect lots of Rage Quits when Zygarde begins to one-shot everything with extreme speed.
