Coat a 13-x 9-inch freezer-safe baking dish with cooking spray and line it with parchment paper.
In a large bowl, mix the graham cracker crumbs with the melted butter until combined. Firmly press the mixture into the bottom of the prepared baking dish, creating an even layer. Freeze until the crust is firm, about 20 minutes.
In another large bowl, beat the cream cheese, lemon zest, lemon juice, and 1 cup of powdered sugar with an electric mixer on high speed until the mixture is fluffy, about 3 minutes.
In a separate large bowl, combine the heavy whipping cream and the remaining 1/4 cup powdered sugar. Beat on high until stiff peaks form, about 2 minutes. Gently fold 1 cup of the whipped cream into the cream cheese mixture.
Spread the cream cheese mixture over the chilled crust and freeze until set, about 30 minutes.
In a large bowl, whisk together the milk and pudding mix until smooth and thickened, about 2 to 4 minutes. Spread the pudding over the cream cheese layer. Chill until the pudding is slightly set, about 45 minutes.
Carefully spread the remaining whipped cream over the pudding layer. Chill, covered, until firm, for at least 4 hours or up to 24 hours. Garnish with lemon slices before serving.
Store any leftovers, covered, in the refrigerator for up to 4 days.