Mix garlic, lemon zest, oregano, rosemary, 1/2 tsp salt and 1/2 cup oil
in small bowl. Season marinade to taste with black pepper.
Toss shrimp in a medium bowl with 3 Tbsp marinade to coat. Cover and refrigerate for at least 1 hour and up to 1 day. Cover and refrigerate remaining marinade; return to room temperature before grilling.
Prepare barbecue for medium-high heat.
Thread shrimp onto flat metal skewers, spacing shrimp apart so they cook evenly.
Gently toss zucchini, squash, asparagus and onions in a large bowl with 3 Tbsp remaining marinade to coat. Thread tomatoes onto additional flat metal skewers.
Brush grill rack with oil. Grill zucchini, squash and onions until golden-brown grill marks form and the vegetables are crisp-tender, about 10 minutes. Grill tomatoes until they begin to burst open and caramelize, about 10 minutes.
Grill asparagus until grill marks form and asparagus is crisp-tender, about 4 minutes. While vegetables grill, brush some of remaining marinade over them and turn vegetables as needed. Transfer vegetables to platter and tent with foil to keep warm
Grill shrimp, brushing with remaining marinade, until they are just cooked through and pink, about 2 minutes per side. Squeeze juice from 1 lemon wedge over shrimp on grill.
Transfer shrimp to platter with vegetables and serve with remaining lemon wedges.