Heat oil in a large pot over high heat. Add pork and cook until no longer pink, about 5 minutes. Add onion, zucchini, and garlic and cook until vegetables are softened, about 4-5 minutes.
Add water, black bean sauce, sugar, and bring the sauce to a simmer. Reduce heat to medium-low, and cook for an additional 5 minutes. Taste the sauce and season with soy sauce if needed.
Add the cornstarch slurry to the sauce and continue to simmer until thickened, about 5 minutes. Season with black pepper and keep warm.
Cook noodles according to package directions. Drain. Portion noodles into bowls and spoon sauce on top. Garnish with sliced cucumbers and fresh bean sprouts. Serve hot.