Preheat the oven to 375 degrees F (190 degrees C).
Press the pie crust into the bottom and up the sides of a 9 inch pie plate. In a large bowl, stir together the Splenda white granular sugar sub., cornstarch and flour. Mix in the lemon zest. Gently stir in the blueberries. Pour into the pie crust. Add the raspberries on top of the blueberry mixture. Then Pour the lemon juice over the blueberry mixture already in pie crust.
In a medium bowl, stir together the Splenda brown sugar blend, oats, flour, and cinnamon. Mix in butter using a fork until crumbly. Spread the crumb topping evenly over the pie filling.
Bake for 50 minutes in the preheated oven, then reduce heat to 350 for 10 more minutes, or until browned on top. Cool over a wire rack.