In a medium bowl, combine the graham cracker crumbs, granulated sugar, and melted unsalted butter. Stir until the mixture is evenly moistened and resembles wet sand. Press this mixture into the bottom and up the sides of a 9-inch pie dish, then chill in the refrigerator for about 10-15 minutes.

In a large mixing bowl, beat the softened cream cheese until smooth and creamy, about 1-2 minutes. Gradually add the sweetened condensed milk, freshly squeezed lemon juice, and lemon zest, mixing until well combined.

In a separate chilled bowl, whip the heavy whipping cream on medium-high speed until stiff peaks form, about 3-5 minutes. Gently fold the whipped cream into the lemon mixture.

Carefully pour the lemon filling into the chilled graham cracker crust and smooth the top. Cover with plastic wrap and refrigerate for at least 4 hours, or preferably overnight, to set.

Once set, remove the pie from the refrigerator, garnish with lemon zest or whipped cream, slice, and serve chilled.