The only notable items Porygon-Z actually uses are either that of Choice Scarf, Choice Specs, and Life Orb. All of these using their respective sets and uses. Obviously, the Choice Scarf set is to be used if you want to be a speedy Porygon-Z as you wallbreak, where as Choice Specs is to be used only for Wallbreaking at its finest. As for Life Orb, this item is only to be used with a booster of choice, in Porygon-Z's case being either Agility or Nasty Plot(Basically duplicating the choiced items.) As for a recommendation, I'd suggest the Choice Scarf set just to test it our, but you are more than happy to try the other sets. Here's an import of the set:
Porygon-Z @ Choice Scarf
Ability: Adaptability
EVs: 4 Def / 252 SpA / 252 Spe
Modest Nature
- Tri Attack
- Dark Pulse
- Thunderbolt
- Ice Beam