Place flour, confectioners' sugar, lemon zest and salt in bowl of a food processor and pulse until combined. Add butter and shortening and pulse until mixture resembles coarse crumbs. Add water, one tablespoon at a time and pulse just until dough comes together (be careful to not over mix). Pat dough into a disk and wrap in plastic wrap. Chill at least 30 minutes.

Roll out dough on a lightly floured surface to a 12-inch circle. Gently transfer dough to a 9 1/2-inch pie plate. Fold under edge of dough and crimp to make a decorative crust. Chill at least 30 minutes in refrigerator.

Preheat oven to 400°F. Line pie shell with aluminum foil or parchment paper and fill with pie weights or dried beans. Bake 20 minutes, remove foil and weights and continue to bake about 10 minutes or until lightly golden.

While pie shell bakes, make filling. Place 3 cups blueberries and sugar in a medium saucepan. Stir cornstarch and water together until blended and add to blueberry mixture. Heat to a boil over medium-high heat, stirring frequently to prevent scorching. While blueberries cook and soften, mash about half berries with a potato masher or fork. Boil 1 minute, stirring constantly. Remove from heat. Stir in lemon juice, nutmeg and remaining 3 cups blueberries.

Spoon blueberry mixture into crust and let sit at room temperature 2 hours to set.