Heat the Oil: In a large skillet, warm 2 tablespoons of olive oil and ½ tablespoon of butter over medium-high heat until they're melted and begin to sizzle, about 1–2 minutes.

Sauté the Zucchini: Once the oil is hot, add the sliced zucchini and season them lightly with salt and pepper. Cook for about 3–4 minutes, turning occasionally until they become tender and slightly golden.

Cook the Onion: In the same skillet, add the remaining ½ tablespoon of butter and let it melt. Toss in the diced onion, cooking for about 2 minutes until they soften and become fragrant.

Add the Mushrooms: Incorporate the diced mushrooms into the skillet, stirring them well with the onions. Allow them to cook for 5–7 minutes, stirring occasionally, until they're browned.

Flavor with Garlic and Herbs: Once your mushrooms are beautifully browned, add the minced garlic and herbs to the skillet. Cook for about 20 seconds, stirring constantly, until the garlic becomes fragrant.

Combine and Simmer: Return the cooked zucchini to the skillet with the onion and mushroom mixture. Pour in ½ cup of vegetable broth and toss everything together gently. Allow the mixture to simmer for about 2 minutes.

Final Seasoning and Garnish: Adjust the seasoning with salt and pepper to your liking. Remove from heat, sprinkle with fresh parsley and ¼ cup of grated Parmesan cheese.