Combine chicken broth, onion, garlic, and zucchini in a large pot over medium heat and bring to a boil. Lower heat, cover, and simmer until tender, about 20 minutes.**For Instant Pot, combine all the ingredients and set to 5 minutes, manual high pressure. After cook time, switch to quick release and follow the rest of the instructions!
Remove from heat and purée with an immersion blender, or in batches in a regular blender. Add the yogurt, and herbs (if using) and purée again until smooth.
Sprinkle with salt and pepper and adjust to taste.
Eat it plain, or squeeze in some lemon and add crab, Parmesan cheese, and drizzle with a delicious olive oil.