It's basically just a tomato sauce of onions, olive oil, tomatoes, and sugar, all softened down together. Bring it to a boil with water and add in the zucchini along with dill.
Cook until done, about 20 minutes.
Ehh. Not my thing. The flavors are nice and all of that, this just wouldn't be a soup that I would choose to eat/make/order in a restaurant.
onion -- $.70
zucchini -- $1.35
tomato -- $2.15
Total Cost of Kolokythia Yakhni: $4.20
($2.10 per serving)