Cut the ends of the zucchini and taste them (to make sure you don't have a bitter zucchini).
put water and add some salt to boil, like 2-3 cups of water to boil and add chopped pieces of zucchini (2-3 in pieces since you are going to blend them anyway) let it boil for like 4 minute.
take the zucchini out, put it in the blender (except 2 chunks), add some of its water and blend it well.
In a medium soup pot, add the butter and melt it, add the onion and fry it quick in the butter.
Add the zucchini and the water and let it boil, as soon as it boils add some pepper and chicken bouillon, add the milk and let it boil again, turn it off. To serve add little chunks of the zucchini that you did not blend, (cut those pieces in little squares.).
If you want to make the soup richer, add more milk to water ratio, use whole milk, double the butter used to fry the onion -- you can make this recipe as light or heavy as you want -- (i like it light) ;).