1. FOR THE FILLING: Whisk the zest and yolks in a medium nonreactive bowl until tinted light green, about 2 minutes. Beat in the milk, then juice; set aside at room temperature to thicken (about 30 minutes).
2. FOR THE CRUST: Adjust an oven rack to the middle position and heat the oven to 325 degrees.
3. In a food processor, process the graham crackers until evenly fine, about 30 seconds (you should have 1 cup crumbs). Add the sugar and pulse to combine. Continue to pulse while adding the warm melted butter in a stead stream; pulse until the mixture resembles wet sand. Transfer the crumbs to a 9-inch glass pie plate and, following illustration 1 on page 197, evenly press the crumbs into the pie plate, using your thumb and a ½ cup measuring cup to square off the top of the crust. Bake the crust until it is fragrant and beginning to brown, 15 to 18 minutes; transfer to a wire rack and cool completely.
4. Pour the lime filling into the crust; bake until the center is set, yet wiggly when jiggled, 15 to 17 minutes. Return the pie to a wire rack; cool to room temperature. Refrigerate until well chilled, at least 3 hours. (The pie can be covered directly with lightly oiled or oil-sprayed plastic wrap and refrigerated up to 1 day.)
5. FOR THE WIPPED CREAM: Up to 2 hours before serving, whip the cream in the chilled bowl of an electric mixer to very soft peaks. Adding the confections' sugar 1 tablespoon at a time, continue whipping to just-stiff peaks. Decoratively pipe the whipped cream over the filling or spread the whipped cream evenly with a rubber spatula. Garnish with optional sugared lime slices and serve.