Step 1: Marinate the pork. Place the pork in a large bowl, add the cornflour and toss well to coat. Stir through the Shaoxing and soy sauce, then marinate for 10 minutes to 1 hour.
Step 2: Cook pork and veg. Heat half the oil in a wok over high heat. Sear the pork in batches, until just browned, then set aside. Heat the remaining oil in the wok over high heat. Add the onion, cook for 1 minute, tossing. Stir in ginger, garlic and chillies, cook for 30 seconds, stirring. Add the zucchini and cook until starting to soften.
Step 4: Finish and serve. Return the pork to the wok and stir in the hoisin and fish sauce. Toss well to combine. Finish with a drizzle of sesame oil and remove from the heat. Serve immediately with steamed rice.