Toxic Zombies are extremely fast and dangerous special enemies that explode on death and leaving behind an acid pool. Distance is key when fighting these enemies because if they are in a pack and explode on top of you, it will cause a chain explosion, possibly killing you instantly. Their explosion does damage to other zombies and will cause other Toxic Zombies to explode if near them, so you have options of whether you want to take these enemies out as they come, or group them, gain distance, then explode the entire horde in one shot.