Preheat the oven to 425 degrees F. In a large bowl, combine peach slices, sugar, cornstarch or tapioca and lime zest. Toss the mixture until the peaches are evenly coated, then pour into the prepared chilled pie shell.
Cover the fruit with the prepared, chilled top crust, shape as desired. Chill the shaped pie for at least 20 minutes.
Brush the top of the chilled pie with egg wash just before baking. Sprinkle with sugar and bake at 425 degrees for 15 minutes, rotatin the pie halfway through. After 15 minutes, lower the oven temperature to 375 degrees and continue baking for 30 to 40 minutes, rotating again halfway through. Bake until the top is golden brown and the filling is bubbling all over.