Place bottom crust into a 9 inch pie pan. In a medium bowl, crumble remaining pie crust into a bowl with the brown sugar and 1 tablespoon lemon zest. Mix with hands until dough becomes pea-size crumbs. Set aside.
In a large bowl, combine blackberries, white sugar, flour and 1 tablespoon lemon zest. Fill bottom pie crust with blackberry mixture. Sprinkle crumb topping over mixture and dot with butter.
Bake pie in preheated oven for 45 minutes to 1 hour, or until crust is browned and berries are bubbling. Let stand before serving.