Cut a small sliver from the bottom of each zucchini so it will lie flat without rolling over. Cut a larger sliver from the top to expose the insides of the zucchini. Use a spoon to carefully hollow out the zucchini, being careful not to break all the way through the skin.
Coarsely chop the zucchini insides. Mince the garlic.
In a nonstick skillet, brown the sausage. Drain well.
Mix the chopped zucchini, sausage, and garlic. Stir in the diced bread and moisten with the chicken broth. Season with salt and pepper to taste.
Divide the stuffing mixture among the 4 hollowed-out zucchini. Place them in a shallow microwave-safe baking dish. Add 2 tablespoons of water and cover with plastic wrap.
Microwave 4-5 minutes, until zucchini is tender. Let stand 2-3 minutes before serving.