In a medium bowl, mix together the graham cracker crumbs, sugar, melted butter, and lemon zest. the texture should resemble wet sand. Use he bottom of a glass measuring cup to to press the crust into an even layer over the bottom and up the sides of a pie plate. Place the oven in the pie plate and bake until the crust firms and browns lightly, 10 to 12 minutes. Remove it from the oven and set it aside to cool; keep the oven on.