Begin by washing and chopping all your vegetables. Cut the zucchini into strips, slice the carrots, chop the onion, and quarter the mushrooms. Having everything ready to go will make the cooking process smooth and efficient.
In your wok or large skillet, melt the unsalted butter and add the vegetable or olive oil over medium-high heat.
Once the butter has melted and the oil is hot, add the minced garlic and chopped onion. Sauté for about 2 minutes, stirring frequently until the onion becomes translucent and the garlic is fragrant.
Add the zucchini, carrots, broccoli, and mushrooms to the pan. Stir well to combine all the ingredients. Sauté for about 5-7 minutes, or until the vegetables are tender but still crisp.
Drizzle the soy sauce and teriyaki sauce over the vegetables. Stir to coat everything evenly. Season with salt and pepper to taste. Continue to cook for another 2-3 minutes to let the flavors meld.
Remove the pan from heat. If desired, sprinkle sesame seeds on top for a delightful crunch and a touch of elegance. Serve hot, either as a side dish or over a bed of rice or noodles.