ElectricRock
Electric and Rock types: weaknesses, resistances and Pokémon
Electric and Rock Pokémon take quadruple damage from Ground moves, take double damage from Water, Grass and Fighting moves and resist Flying, Normal, Fire, Electric and Poison moves.
The balance is even: 4 weaknesses and 5 resistances or immunities.
Electric moves are super effective against Water and Flying and not very effective against Grass, Electric and Dragon. Rock moves are super effective against Fire, Ice, Flying and Bug and not very effective against Fighting, Ground and Steel.
To beat these Pokémon, your best pick is Ground moves. Avoid Flying, Normal, Fire and Electric moves, which deal little or no damage.
There is 1 Pokémon with this combination, such as Iron Thorns.