Grilled Garden Vegetable and Prosciutto Salad

Ingredients

• 2 ears corn
• 1 (8 ounces) medium zucchini, cut lengthwise in quarters
• 1 head romaine, cut lengthwise in quarters leaving core intact
• 1 medium red onion, quartered leaving core intact
• 4 slices prosciutto, cut into strips
• 6 tablespoons olive oil, divided
• 3 tablespoons lime juice
• 2 tablespoons chopped mint leaves
• 1 teaspoon lime zest
• ½ teaspoon kosher salt
• ½ teaspoon sugar