Bring 4 cups of water to a boil in a medium-sized saucepan.
Cook broccoli, carrots and zucchini for 4 minutes; drain.
Pat broccoli mixture dry with paper towels; roughly chop so that fritter can hold together when formed. Place broccoli mixture and flour in a large bowl; stir to coat.
Stir in cheese, salt, pepper, cumin, garlic salt, chili powder, and onions into the broccoli mixture. Stir in the whisked egg until the broccoli mixture is evenly combined.
Heat a large nonstick skillet over medium heat. Add oil to pan; swirl to coat.
Form 1/2 cup of the broccoli mixture by hand into a ball.
Add ball into a pan and flatten slightly with a spatula; cook 3 to 4 fritters at a time. Cook each fritter 4 minutes on each side or until golden brown.
Transfer to a plate with a paper towel to soak up the excess oil. Repeat procedure for the rest of the fritters.
Avocado Yogurt Sauce
In a blender, combine yogurt, avocado, dill and chives in a small bowl. Serve yogurt mixture with fritters.