Beef, Summer Squash and Sweet Potato Curry

2 cups water

1 lb lean (at least 80%) ground beef

1 medium onion, chopped (1/2 cup)

1 tablespoon grated gingerroot

2 tablespoons curry powder

1 teaspoon ground cumin

1 teaspoon salt

1 large sweet potato, peeled, cut into 1/2-inch cubes (3 cups)

1 can (14 1/2 oz) diced tomatoes, undrained

1 cup Progresso® reduced-sodium chicken broth (from 32-oz carton)

2 medium zucchini, cut in half lengthwise, then cut crosswise into 1/2-inch slices (2 cups)

1/2 cup plain yogurt