In a small bowl, whisk together soy sauce, oyster sauce, ginger, rice vinegar, brown sugar, garlic, sesame oil, Sriracha, and black pepper until well combined.

Cut the salmon fillet into 1-inch chunks and prepare fresh pineapple, red onion, and zucchini by slicing them into uniform pieces. Thread the salmon, pineapple, red onion, and zucchini onto skewers.

Let the assembled kabobs marinate for 10 to 15 minutes at room temperature while preparing the grill.

Preheat the grill to medium-high heat, around 400°F (200°C). Lightly oil the grill grates.

Place the marinated kabobs on the grill and cook for 5 to 7 minutes, turning occasionally.

Pour the reserved marinade into a small saucepan, bring to a boil, then reduce and simmer for 5 to 6 minutes until thickened.

Once cooked, remove the kabobs from the grill, drizzle the thickened marinade, and garnish with fresh cilantro if desired.