Slice the kernels off the corn and place in a large bowl. Add zucchini, squash, jalapeno, green onions, basil, salt and pepper. Add egg and mix until evenly combined. Keep sprinkling in flour until the batter is moist, but more vegetables than batter. Set aside to rest for 10 minutes.
While the batter rests, make the crema by combining the avocado, yogurt, lime juice, and salt in bowl. If you want this more pureed blend in blender.
In a large skillet over medium heat, heat olive oil. Working in batches, measure about 1/4 cup the batter for each fritter and drop in the pan, lightly pressing with a spatula. Cook 3-4 fritters at a time, 4-5 minutes until the edges are lightly browned then flip and cook other side about 3-4 minutes. Place cooked fritters on a paper towel lined plate. Serve fritters warm served with crema and fresh basil.