Soak wooden skewers in water for 20 minutes to prevent burning during the grilling process.
Cut the pork tenderloin, pork belly, zucchini, and red bell pepper into uniform 1-inch cubes for even cooking.
Whisk together the gochujang, tamari, rice vinegar, grated ginger, minced garlic, and toasted sesame oil in a small bowl.
Thread the pork and vegetables onto the skewers, alternating the lean tenderloin with the rich pork belly for balanced texture.
Preheat a grill pan or outdoor grill to medium-high heat and lightly brush with a high-heat cooking oil.
Grill the skewers for 3-4 minutes per side, turning frequently to ensure even browning and charring.
Brush the skewers generously with the spicy gochujang glaze during the final 2 minutes of cooking.
Remove the skewers from the heat once the pork is cooked through and the glaze is beautifully caramelized.
Sprinkle with sliced green onions and toasted sesame seeds before serving hot.