Iron Treads @ Leftovers / Assault Vest 
Ability: Momentum  
EVs: 252 HP / 4 SpD / 252 Spe  
Jolly Nature  
- Rapid Spin  
- Earthquake  
- Knock Off / Ice Spinner 
- Rollout
Iron Treads is a great counter to magnezone as it resists both of its STAB moves, Rollout allows it to pivot to another teammate, while momentum allows it to keep itself healthy. There is very little Magnezone can really do to Iron Treads while Iron Treads can slowly whittle it down with knock off while recovering health with Leftovers and Momentum