Heat a wok/large skillet over medium high heat. Once it is hot, add in the black bean paste, oyster sauce, and sugar to 2 tbsp oil and fry for a few minutes, while breaking apart the sauce. Mix in the scallions. Pour into a bowl and set aside.
Clean your wok/skillet, and stir fry the beef in 1 tbsp of neutral oil. (I like to cook it until it’s at medium, because or else it will taste too rubbery). Season with salt and pepper. Scoop onto a plate and set aside.
Using the same wok/skillet, cook the zucchini and onion with the remaining 1 tbsp of oil for a few minutes. Make a space in the center of the wok/skillet and add back in the sauce. Mix everything together.
Add back in the cooked beef and water and let it come to a boil. Pour in the cornstarch slurry and stir. Keep stirring until the sauce has become thick and glossy. At this point, you can add more sugar if necessary according to your liking.
Cook the noodles and drain. Rinse under cold water for a chewier texture.
Pour the sauce over the noodles and garnish with the cucumber strips. Mix well and enjoy!