Place the skillet back over medium heat, add oil and sauté the marinated pork from the first step.
After a few minutes, add shrimp (optional) and sauté for a few minutes then transfer to a plate and set aside.
Place the skillet back over medium-high heat, add the remaining oil and sauté onion for 3 to 4 minutes.
Add zucchini and continue to sauté for another 2 to 3 minutes.
Pour the pork and shrimp or pork only mixture back into the skillet and continue to sauté for 2 to 3 minutes.
Stir the toasted black bean paste from earlier into the meat and vegetable mixture until everything is evenly coated.
Add water a little at a time until the mixture is smooth and simmering.
Add cornstarch slurry and stir together to thicken the sauce. Remove from heat and keep warm.
To cook the noodles, fill a large pot with water and place over high heat. Once the water begins to boil, add noodles and cook through, stirring occasionally. After about 5 to 6 minutes, the noodles will be cooked but still a bit chewy. Drain the noodles and rinse gently. Divide noodles into bowls for serving and top each with the warm sauce.
Mix the noodle and sauce together and there you have it!