►Combine garlic, parsley, basil, red pepper flakes, olive oil, balsamic vinegar, salt, and pepper in a medium bowl and set aside.
►Heat a grill to medium. Slice zucchini thinly using a vegetable peeler. Grill zucchini strips 1 to 2 minutes per side, just until grill marks appear. Transfer grilled zucchini to the bowl with the marinade. Toss to coat, cover bowl, and refrigerate 2 hours.
►Dress arugula with olive oil, salt, and pepper to taste.
►Grill pumpernickel bread until just toasted. Spread 1 tablespoon pesto on each slice of bread. Top 4 slices of bread with equal amounts asiago, marinated zucchini, roasted red peppers, and baby arugula. Add remaining slices of bread and press to close. Serve immediately.