This delicious guacamole recipe replaces half the amount of high-calorie avocado in a traditional guacamole recipe with a stealth, low-calorie vegetable--zucchini--to cut 100 calories and 6 grams of fat so we can eat more guacamole with fewer calories. We use the microwave to cook the zucchini until it's very tender, but you can steam it on the stovetop if you prefer.