Split Pea Zombie Soup can be very difficult to get, as only players will count, not Spawnable Zombies. The best place to get it is in Gardens & Graveyards due to the length of the game, but it is easier if the plants are bad at defending, as the game will last longer. Try to attack weakened zombies with headshots to use the least ammo and maximize amount of damage you get out of each use of the ability. You can also do this in Suburbination, as multiple players will try to get to a base, so use this to your advantage. It is recommended not to use the Retro Gatling, as it has half the ammo and fires much slower. As a different strategy, try to invite a friend to a multiplayer match. Your friend can weaken zombies with their primary weapon while you finish them off by shooting them down. The only plant that won't work very well here is Cactus and her variants when they use their Drones, because sometimes if the drones attack players too far away for you to shoot with your Pea Gatling, you will have to focus on attacking other viable zombies until the Drone is destroyed.