I deal with zoning is by zoning myself lol
Think of Falco Spamming aerial blasters (Falco can stun characters with it's blasters, on the other hand, Fox does damage without stun but it can fire faster than falco) to zone itself from Close-Range characters, on ground level, just sidestep upon its shots and you'll directly go close to him. With Pikachu however, it has Thunder so getting close to it will force it to use thunder. Just time its Thunder and the delay it'll take before the Thunderbolt hits the ground to stop its thunder from working or if you can, block it. To be honest, there's no actual way to counter zoning since it depends on the character the both of you uses.