Preheat the oven to 200°C or 400°F. Line a baking tray with parchment paper. Set aside.
Start by preparing and slicing the zucchini and crushing the pistachios if you have the whole ones.
To make the whipped ricotta: Place the ricotta, olive oil, salt and pepper in a blender. Blend all the ingredients until you get a creamy texture.
Score a border around the puff pastry of about 0.5cm.
Spread the ricotta over the puff pastry, leaving the border empty. Sprinkle the pistachios on top and layer on top by overlaying the zucchini.
Brush the zucchini with olive oil and season with a pinch of salt and sumac.
Bake for 30 minutes, until the pastry has browned and the zucchini are cooked through. Slice the tart into six and serve.