1. In a bowl, combine the basil with 2 tablespoons of the olive oil and the garlic. Season lightly with salt and pepper. Add the shrimp and turn to coat.
2. In a shallow bowl, generously brush the zucchini slices on both sides with olive oil and season with salt and pepper; let stand for 5 minutes to soften.
3. In a skillet, cook the bacon over moderate heat until lightly browned, about 2 minutes per side. Drain.
4. Working at the tip of a 12-inch skewer, pierce the very end of a zucchini slice. Swing the zucchini to the side and skewer a shrimp, then loop the zucchini slice around the shrimp and pierce the zucchini slice to secure it around the shrimp. Add another shrimp, wrap the rest of the zucchini slice around it and secure it on the skewer. Add a bacon square. Repeat the threading, using 2 more zucchini slices, 4 more shrimp and 2 more bacon squares. Thread the remaining ingredients to make 8 skewers.
5. Light a grill or preheat a grill pan. Oil the grill and grill 4 skewers at a time over high heat for about 2 minutes per side, or just until the shrimp are cooked through and the zucchini are still crunchy. Serve hot.