Preheat oven to 375° F. Position a rack in lower third of oven. Slice each pear quarter into bite-size pieces and place them in a large mixing bowl. Add the zest, sugar, flour, and ginger; toss gently. Spoon the fruit into the prepared crust. To make the crumble topping, combine the reserved crust mixture, flour, brown sugar, and cinnamon in a small bowl. Sprinkle over the pear filling and bake until the topping is golden brown and the fruit is tender, 50 to 55 minutes. Let cool before slicing.