If using wooden skewers, soak them in water for at least 20 minutes to prevent burning.
Cut the pork tenderloin and pork belly into 1-inch cubes. Slice the zucchini into rounds and the red bell pepper into 1-inch squares.
In a small bowl, whisk together the gochujang, tamari, rice vinegar, sesame oil, garlic powder, and ginger powder until smooth.
Place the pork cubes in a bowl and toss with half of the gochujang marinade, sea salt, and black pepper.
Thread the skewers, alternating between pork tenderloin, pork belly, zucchini, and red bell pepper.
Preheat a grill or grill pan over medium-high heat. Lightly oil the grates.
Place the skewers on the grill and cook for 3-4 minutes per side, brushing with the remaining marinade during the last 2 minutes of cooking.
Ensure the pork is cooked through and the vegetables are tender with a slight char.
Remove from the heat, sprinkle with sesame seeds, and serve immediately.