01 - Preheat oven to 350°F. Prepare a 9x13 inch baking dish by lightly greasing or lining with parchment paper.
02 - In a medium bowl, combine flour, softened butter, and powdered sugar. Blend until the mixture resembles coarse crumbs. Press firmly and evenly into the bottom of the prepared baking dish.
03 - Bake for 18 to 20 minutes, or until the edges are lightly golden. Remove from the oven and allow the crust to cool completely before adding layers.
04 - Using an electric mixer, beat the softened cream cheese and powdered sugar on medium speed until smooth and creamy. Gently fold in the whipped topping until fully incorporated. Spread the mixture evenly over the cooled crust.
05 - In a bowl, whisk together both packages of instant lemon pudding mix and cold milk for approximately 2 minutes until thickened. Stir in lemon zest if using. Allow the pudding to rest for 5 minutes to fully set, then spread evenly over the cream cheese layer.
06 - Spread the remaining whipped topping evenly over the lemon pudding layer, smoothing the surface with a spatula.
07 - Sprinkle lemon zest over the top for garnish if desired. Refrigerate for at least 2 hours, preferably 3 or more, until fully chilled and set. Slice into squares and serve.