Bring a large saucepan of water to a boil. Add the corn and simmer, uncovered, until the kernels turn slightly darker yellow, 5 to 6 minutes. With tongs, remove the corn from the water and let cool. Cut the kernels off the cobs; discard the cobs and reserve the kernels.
Bring the saucepan of water to a boil again. Add the fresh shelling beans and simmer until tender, 25 to 30 minutes. If you are using frozen lima beans, simmer for 5 minutes. Remove with a slotted spoon and cool.
Bring the same saucepan of water to a boil. Add 1 tsp. salt and the string or wax beans and simmer until almost tender but still very crisp, about 4 minutes. Add the zucchini and simmer for an additional 2 minutes. Drain and cool.
Place the butter or lima beans, string or wax beans, corn, zucchini, peppers, and onions in a large bowl.
In a small bowl, whisk together the lemon juice, olive oil, and canola oil. Season with salt and pepper. Add the dressing and basil to the bean and corn mixture and stir together. Place the salad in a large serving bowl and serve.