Stir graham crumbs, sugar, and melted butter in a bowl until evenly moistened and sandy.
Press the mixture firmly into a 9-inch pie plate, pushing up the sides to form an even crust.
Chill the crust until set, about 30 minutes (or freeze 10 minutes for a quick set).
Beat cream cheese in a mixing bowl until smooth and fluffy, scraping the bowl as needed.
Stream in the condensed milk and mix until silky with no lumps.
Whisk in lemon juice, lemon zest, vanilla, and salt until the filling slightly thickens.
Pour filling into the chilled crust, smooth the top, and refrigerate 4–6 hours until firm.
Whip heavy cream with powdered sugar to soft peaks; spread or pipe over pie and garnish with zest.