Preheat your oven to 375°F (190°C).
Cut the zucchinis in half lengthwise and scoop out the seeds with a spoon to create 'boats.' Set the zucchini halves aside.
In a large skillet, heat olive oil over medium heat. Add minced garlic and sauté for about 1 minute until fragrant.
Add diced mushrooms to the skillet and cook for 5-7 minutes until they soften. Then, add the chopped spinach and cook until wilted, about 2-3 minutes.
Remove the skillet from heat and let the mixture cool slightly. In a mixing bowl, combine the sautéed mixture with ricotta cheese, salt, pepper, and Italian herbs. Mix well until combined.
Stuff each zucchini half with the ricotta and vegetable mixture. Place them in a baking dish, cut side up.
Sprinkle the stuffed zucchinis with shredded mozzarella cheese and Parmesan cheese if desired.
Cover the baking dish with aluminum foil and bake for 20 minutes. Then, remove the foil and bake for an additional 10 minutes until the cheese is golden and bubbly.
Once done, remove from the oven and let cool for a few minutes before serving.