Add the peaches, blueberries, lemon zest, cornstarch, and sugar to a medium sized bowl and mix until combined.
For the crumble, add the brown sugar, flour, oats, pistachios, cinnamon, and melted butter to a bowl and mix until combined and crumbles form.
Add the peach and blueberry mixture to a wide baking dish, then evenly spread the crumble on top.
Bake for 30 minutes at 350°F, or until it turns golden and top crisps up.
Serve with vanilla ice cream.
