Every farm has a few pitch forks laying around, and can be used like a combat trident. Usually, the handle’s made of wood, has a handle grip, and 4 spikes on the same line. You’ll have to get physical and charge zombies one by one and aim for the head. Alternatively, you could first trip the zombie and then head-stab him while he’s on the ground. It’s a long range weapon, and you should never engage more than one zombie at the time because it’s hard to handle, effective trident blows require a lot of push force and can leave you defenseless for some time as you’re committed to a blow.