Thaw shrimp and scallops, if frozen. Rinse shrimp and scallops and pat dry with paper towels.
On 4 long metal skewers, alternately thread shrimp, scallops, sweet pepper, onion, and zucchini, leaving about 1/4 inch between pieces.
In a small bowl combine chipotle peppers, lime juice, oil, brown sugar, salt, cumin, and garlic. Brush kabobs with chipotle mixture.
Grill kabobs on the greased rack of an uncovered grill directly over medium coals for 5 to 8 minutes or until shrimp and scallops turn opaque and vegetables are crisp-tender, turning occasionally to cook evenly.
Sprinkle kabobs with cilantro and serve with lime wedges.