For the salad: Heat a grill pan over medium-high heat or preheat a gas or charcoal grill. In a large bowl add the romaine lettuce, corn, zucchini, and shrimp and drizzle with olive oil. Season with salt and pepper, to taste. Grill the romaine lettuce, turning occasionally, until crisp-tender and browned in spots, about 2 minutes. Coarsely chop the grilled lettuce and add it to a large salad bowl. Grill the corn and zucchini for 2 minutes on all sides until crisp-tender. Remove the kernels from the corn and add to the salad bowl. Chop the zucchini into 1/2-inch pieces and add to the bowl. Grill the shrimp until the meat is opaque and cooked through, about 2 to 3 minutes on each side. Cool slightly and cut into 1/2-inch pieces. Add the chopped shrimp, butter lettuce, tomatoes, and avocado to the bowl.
For the dressing: In a small bowl, whisk together the lemon juice, olive oil and agave nectar until smooth. Season with salt and pepper, to taste.
Pour the dressing over the salad and toss until all the ingredients are coated. Garnish the salad with tortilla strips and serve.