Preheat your oven to 375°F (190°C).

In a large skillet, heat the olive oil over medium heat. Add the zucchini and bell pepper; sauté until softened (about 5-7 minutes).

Add the minced garlic and cook for another minute, then add in the spinach until wilted. Season with salt, pepper, and Italian seasoning if desired.

In another saucepan, melt the butter over medium heat. Whisk in the flour and cook for 1-2 minutes until it’s lightly golden.

Gradually add the milk, whisking constantly until the sauce thickens (about 5-10 minutes). Stir in half of the Parmesan until melted and season with salt and pepper.

Spread a thin layer of the creamy sauce on the bottom of a baking dish. Layer three lasagna noodles, followed by half of the ricotta cheese, half of the sautéed veggies, and a third of the mozzarella cheese. Repeat the layers, finishing with the last noodles topped with remaining sauce and mozzarella.

Cover with foil and bake in the preheated oven for 25 minutes. Remove the foil and bake for another 15 minutes until the top is golden and bubbly.

Let it cool slightly before slicing and serving. Enjoy your delicious creation!