Prepare yogurt cheese a day before needed.
Stir yogurt and ricotta together and place in a cheese cloth (or large paper coffee filter) in a strainer.
Place strainer over a bowl, wrap loosely with plastic wrap and chill for 24 hours. Discard whey (liquid in bowl), and refrigerate yogurt cheese until ready to use.
For the crust: preheat oven to 325 F (160 F).
Combine graham cracker crumbs, lemon zest, salt and melted butter and press into an ungreased 9-inch (22 cm) pie plate.
Bake for 10 minutes, then cool while preparing filling.
For filling, stir yogurt cheese with honey, egg, lemon zest and vanilla.
Spoon into cooled pie shell and bake for 30 minutes. Cool to room temperature, then chill at least 4 hours before serving.
Top with diced mango immediately before slicing.