Heat vegetable oil and butter (salted or unsalted) in a large wok over medium-high heat.
Add minced garlic and minced ginger and sauté for 4-5 seconds.
Add zucchini (cut into batons), thinly sliced onions, broccoli florets, and sliced button mushroom, and saute for a minute.
Now add salt, black pepper, and dark soy sauce and mix well.
Cook uncovered for 6-8 minutes until the liquid released by the vegetables is evaporated and the vegetables are slightly charred, stirring frequently. Serve hot.