Begin by combining the graham cracker crumbs with melted unsalted butter in a mixing bowl. Stir until the crumbs are evenly coated and press into the bottom of a trifle dish.

In a chilled mixing bowl, whisk the heavy whipping cream using an electric mixer on medium-high speed until stiff peaks form, approximately 2-3 minutes. Set aside.

In a large mixing bowl, beat softened cream cheese until smooth. Gradually add powdered sugar, key lime juice, lime zest, and vanilla extract, mixing until fully blended.

Gently fold the whipped cream into the cream cheese mixture using a spatula until combined and fluffy.

Spoon half of the creamy mixture over the crust, spreading it evenly. Layer extra graham cracker crumbs and repeat with remaining lime mixture and crumbs.

Cover with plastic wrap and refrigerate for at least 120 minutes before serving. Top with extra graham cracker crumbs and fresh lime zest just before serving.