Sigh! It's going to be a loooooooong next couple of years.
One word of caution, though. If you're crying in your soup, ease up on the kosher salt. You won't need as much!
Rinse leeks well with cold water. They can be very sandy. Pat with paper towels to dry.
Heat the butter and oil in a large stockpot, add the leeks, and saute over medium-low heat for 5 minutes.
Add the potatoes, zucchini, chicken stock, salt, and pepper; bring to a boil; then lower the heat and simmer for 30 minutes.
Cool for a few minutes and then process through a food mill fitted with the medium disc. Add the cream and season to taste.
Serve either cold or hot, garnished with chopped chives and/or zucchini.