Preheat the oven to 425°F. If you have a convection setting, this is a good time to use it for even browning, but it will also work without it.

Cut the zucchini in half lengthwise. Cut each half into 3 to 4 planks, each about ¼-inch thick. Lay the zucchini on parchment-lined baking sheets. Brush the zucchini with the olive oil and sprinkle with salt, black pepper, and red pepper flakes. Bake the zucchini in the preheated 425℉ oven until they are browned and tender, 20-25 minutes. Once baked, remove them from the oven and reduce the heat to 350°F.

In a skillet, melt the butter over medium heat. Add the breadcrumbs, Italian seasoning, and ½ cup Parmesan cheese. Gently stir and toast the breadcrumbs until they are golden, 6-8 minutes. Once toasted, remove them from the heat.

Grease a 9 x 13-inch baking dish. Spread about ¾ cup of the prepared tomato pasta sauce on the bottom of the dish in an even layer. Place about half of the zucchini pieces in a single layer. Tear half of the slices of mozzarella cheese over the zucchini. Layer on half of the soppressata. Spread half of the remaining sauce and sprinkle with half of the breadcrumb mixture. Repeat these layers one more time, ending with the breadcrumbs and ¼ cup Parmesan cheese.

Bake the dish in the preheated 350°F oven until the sauce is bubbling throughout, 45-55 minutes. Remove the baking dish from the oven and allow it to rest for 15 minutes before slicing and serving.