Preheat oven to 350 degrees F. Remove crust from freezer and let thaw for 5 minutes.
Meanwhile in a bowl, whisk together lime zest, egg yolks, condensed milk, lime juice and rum. Mix well. It may look like it's starting to separate but mix it well and it will come together. Sprinkle 1/4 cup of the coconut flakes on the bottom of the crust then pour the mixture into the crust and top with the rest of the coconut.
Bake until the center is set, but still jiggles a bit when the pan is nudged, about 20 to 25 minutes. When baked, cool the pie completely on a wire rack. (At this point the pie can be chilled up to a day ahead and topped when you're ready to serve.)
For the topping, beat cream in a bowl with an electric mixer until it just holds stiff peaks. Spread cream over cooled pie; garnish with lime slices. Serve immediately.