In a medium bowl, whisk together the gochujang, tamari, honey, sesame oil, rice vinegar, minced garlic, and grated ginger to create the marinade.
Cut the pork loin into 1-inch cubes and toss them in the marinade until well coated, allowing them to sit for at least 15 minutes.
Slice the zucchini into thick rounds and the red onion into wedges suitable for skewering.
Thread the marinated pork, zucchini, and red onion onto skewers, alternating between the meat and vegetables.
Preheat a grill or grill pan over medium-high heat and lightly grease with a high-smoke point oil if necessary.
Grill the skewers for 3-4 minutes per side, or until the pork is cooked through and the vegetables are beautifully charred.
Remove from heat and garnish with sesame seeds and thinly sliced green onions before serving.