Combine crushed graham crackers and melted butter in a bowl until it resembles wet sand.
Press 2 tablespoons of the mixture into the bottom of each cupcake pan cavity.
Freeze the crusts for 10 minutes to set.
Whisk the sweetened condensed milk and key lime juice together in a large bowl.
Gently fold in the fresh lime zest and whipped heavy cream until smooth.
Divide the filling evenly into the prepared crusts.
Chill in the refrigerator for at least 4 hours until firm before serving.