Step 1

Arrange an oven rack in the middle position. Preheat the oven to 375 degrees F.

Step 2

For the white sauce: In the bowl of a food processor fitted with the blade attachment, add the ricotta, feta, eggs, flour, salt and red pepper flakes. Puree until very smooth and creamy. With the machine running, pour in the milk and heavy cream and process until smooth. Transfer to a bowl and set aside. Clean the food processor bowl to use for the pesto.

Step 3

For the pesto: Into the food processor bowl, add the basil, mint, pine nuts, garlic, lemon zest, salt and crushed red pepper flakes. Quickly blend to make a coarse paste. With the machine running, add the olive oil in a steady stream to make a smooth, bright green sauce. Remove the pesto to a bowl and set aside.

Step 4

In a separate bowl, toss together the mozzarella and Parmesan cheeses.

Step 5

To assemble the lasagna: Spread 1 cup of white sauce in the bottom of a 9-by-13-inch baking dish. Top with a single layer of 3 lasagna noodles (see Cook’s Note). Add an even layer of zucchini (parallel to the noodles), 2 tablespoons of pesto in small dollops and one-fifth of the mozzarella cheese mixture. Repeat the process to create a second layer with 1 cup of the white sauce, now 4 noodles, zucchini, 2 tablespoons pesto and another fifth of the cheese mixture. Repeat again, but this time using 3 noodles. Repeat for a fourth layer, using 4 noodles. For the final fifth layer, top with 3 noodles and the remaining white sauce. Sprinkle with the remaining cheese mixture and top with a sprinkling of feta cheese. Tent the baking dish with foil.

Step 6

Bake in the oven until bubbly and the noodles are cooked through, about 35 minutes. Uncover and bake until the sauce is thickened and the top of the lasagna is nicely browned and crusty, about 20 minutes. Remove from the oven and place on a cooling rack for 15 to 20 minutes before cutting into individual portions. Drizzle with the remaining pesto, to serve.

Step 7

The lasagna can be assembled a day ahead and refrigerated. Let return to room temperature, about 1 hour, before baking. Leftover lasagna will keep, covered, in the fridge for 2 to 3 days.