Cut zucchini, tofu, beef, onion, and green onion into bite-sized pieces.
Heat cooking oil in a pot and stir-fry the beef.
Once the beef is cooked, add zucchini and onion, and stir-fry together.
When the vegetables are partially cooked, add tofu.
Add gochujang, minced garlic, soy sauce, and sugar, and mix well.
Pour in water or broth and bring to a boil.
Simmer over medium-low heat until the broth reduces.
Add green onion and simmer once more before serving.