Make the lemon basil vinaigrette. Place all dressing ingredients — 1 ½ cups basil, 1 chopped shallot, 1 clove chopped garlic, ½ cup EVOO, 2 tbsp lemon juice, 1 tsp white wine vinegar, 1 tsp Kosher salt, and a pinch of red pepper flakes — in a blender (personal blenders are the perfect size for sauces and dressings!), then puree until very smooth. Set aside.
Season the zucchini. Place quartered zucchini wedges in a large mixing bowl, then drizzle with 2 tbsp avocado oil, ¾ tsp kosher salt, and ¼ tsp freshly ground black pepper. Toss to thoroughly coat.
Grill the corn and zucchini. Preheat a grill to medium-high. When hot, coat with nonstick grill spray. Place shucked corn and seasoned zucchini wedges directly on grill grates, then cook for 3-4 minutes per side, about 12-14 minutes, or until the corn is charred on all sides and the zucchini is tender and has almost a creamy texture.
Cut the veggies. Allow the corn and zucchini to cool for about 5 minutes, then use a sharp knife to cut the kernels off of each ear of corn. Slice the zucchini into ½ inch pieces. Place in a large mixing bowl.
Assemble the salad. To the zucchini and corn, add ½ cup crumbled feta, ⅓ cup chopped toasted walnuts, and ¼ cup thinly sliced scallions. Drizzle with ¼ cup of basil vinaigrette (or whichever dressing you’re using), then toss to thoroughly coat. Taste and adjust seasoning as needed. Serve immediately or at room temperature with a generous pinch of flaky sea salt. Feel free to top with additional feta, walnuts, or scallions.