It's better to run copper from the house down into the ground then to the zone box. If poly pipe is used it will expand and contract with the weather and eventually start to bulge. Also the poly pipe is not UV rated. That will cause problems a few years down the road. Poly pipe gets damaged easier than copper pipe. Copper pipe will last longer and it looks better. Copper pipe is stronger and will not break when you take the trimmer near it or hit it with the mower. The copper pipe will not bend out of shape over the years. I highly recommend using copper pipe, or UV rated pipe for this place.