Preheat oven to 375°F (190°C).
In a medium skillet, heat olive oil over medium heat and sauté diced onion and minced garlic until translucent.
Add the ground beef to the skillet, browning it thoroughly while breaking it into small crumbles.
Stir in the tomato puree, dried oregano, and half of the salt and pepper, then simmer for 10 minutes to develop flavors.
While the sauce simmers, boil the lasagna noodles in salted water until al dente, then drain and set aside.
In a small bowl, whisk together the ricotta cheese, egg white, and the remaining salt and pepper until smooth.
Thinly slice the zucchini into rounds to act as a moisture-rich vegetable layer.
In a small oven-safe dish, spread a thin layer of meat sauce, followed by a layer of noodles, zucchini slices, and the ricotta mixture.
Repeat the layers, finishing with the remaining meat sauce and a topping of shredded mozzarella cheese.
Cover with foil and bake for 20 minutes, then remove foil and bake for an additional 10 minutes until the cheese is golden and bubbly.