Piping is when they first break through, start moving around and chirping. Zipping is when they start rotating in the egg, breaking around so they can get out. And yes, it can be nerve wracking, seems like it takes forever! It's best whenever possible, to let nature do it's job. Only as a very last resort should help be given. Many feel that you should not help at all, that if they are not strong enough to get out on their own, they are too weak to do well. That is incredibly hard for most humans to do. And helping can sometimes cause damage that isn't survivable, so it has to be done very carefully. I've got eggs in an incubator right now, 4 of them pipped this morning, I can hear them intermittently but no zip yet. Good luck with your hatch!