Combine graham cracker crumbs and granulated sugar in a medium bowl.
Add melted butter and mix until the mixture resembles damp sand.
Press the mixture firmly into the bottom of a 9-inch pie dish.
In a large bowl, whisk together sweetened condensed milk, fresh lemon juice, and lemon zest until well combined.
Fold in the thawed whipped topping until fully incorporated and the mixture is smooth.
Pour the filling into the prepared crust and spread evenly.
Refrigerate for at least 4 hours, or until the filling is set.
Chill for a few more hours for optimal texture before serving.
Serve slices chilled.