In a large pot or dutch oven, brown meat in 2 T olive oil. Remove beef and drippings from pot (keep drippings).
Saute the onions, carrots, and celery in the olive oil and butter. Add potatoes and zucchini, one at a time, cooking each for 2-3 minutes before adding the next. Salt and pepper between each addition, to taste.
Add white beans, green beans, beef stock, and tomatoes. Cover and cook slowly over low heat for at least 3 hours.