Combine the graham cracker crumbs with the melted butter and press the mixture into the bottom of a trifle dish.
In a chilled bowl, whip the heavy cream until stiff peaks form.
In a separate bowl, beat the softened cream cheese until it is smooth. Gradually add the powdered sugar, key lime juice, lime zest, and vanilla extract, mixing well.
Carefully fold the whipped cream into the lime mixture until fully incorporated.
Layer half of the lime mixture over the crust, sprinkle with additional graham cracker crumbs, then repeat the layers. Finish with extra crumbs and lime zest on top.
Place the trifle in the refrigerator to chill for at least 120 minutes before serving.
