It’s really hard to say how long, but it sounds like things are going well.
There is a whole lot going on inside that egg the last few days. The chick has to absorb the yolk, position itself to hatch, dry up blood vessels it no longer needs, do something with that gunk it is in so it dries nice and fluffy instead of matted with gunk, and learn to breathe air instead of living in a fluid environment. They do some of this before internal pip. Some chicks do a lot of this between internal pip and external pip. Some do more of this after external pip and before zip, and some have not totally finished all of this when they zip and come out.
For them to be able to chirp in the egg, they have already successfully done the internal pip and are learning to breathe air. They may wait a day or maybe even two before they external pip while they are doing all that other stuff. In that case they will probably zip pretty soon after external pip. They may external pip pretty darn soon, but you may have a long wait between external pip and zip.
I can’t tell you how long it will be. It could easily be another three days before you see a chick. You may see one before you go to bed tonight.
I know this can be a really stressful time. Try concentrating on the thought that things seem to be going well.