To make the crust:

1. Preheat the oven to 350 degrees.
2. Pulse graham crackers in a food processor to crumbs. Add the remaining ingredients and pulse to combine. Press the mixture into the bottom of a deep-dish pie pan using your fingers. Bake in the oven for 10-12 minutes, or until the crust is set. Set aside to cool slightly.

To make the pie filling:

1. In a large bowl, combine the softened cream cheese and sweetened condensed milk using a hand mixer set at medium speed, beating until smooth. Add in the zest, juice, and sour cream, stirring on low to combine. Spoon the filling into the prepared cooled crust. Cover the pan with a sheet of plastic wrap and place in the fridge to firm up, about 4 hours or overnight. When ready to serve, prepare the whipped cream topping. In a large bowl or the bowl of a stand mixer, whisk the heavy whipping cream on medium speed until frothy and slightly thickened. Add the sugar and continue whisking until thickened to a fluffy cloudlike consistency. Spoon on top of the pie and serve.