Wash and pat dry the zucchini and mushrooms thoroughly. Slice the zucchini into half-moons, about ¼-inch thick, and cut the mushrooms into thick slices, each roughly ½-inch. Thinly slice the onion and mince the garlic for even distribution.

Place a large skillet over medium heat and add olive oil. Allow the oil to heat until it shimmers, about 1-2 minutes.

Add the thinly sliced onions to the hot skillet and sauté for about 3 minutes until soft and translucent.

Stir in the minced garlic and sliced mushrooms. Cook for 3-4 minutes, stirring regularly until the mushrooms begin browning.

Gently fold the sliced zucchini into the skillet and season with salt, black pepper, and optional dried thyme. Sauté for an additional 3-5 minutes until the zucchini is tender yet firm.

Taste and adjust seasoning as necessary, then toss in fresh parsley before serving warm.