Preheat the oven to 350 degrees. Grease a wide, 2-quart baking dish, or spray it with nonstick spray.
Put the zucchini in a colander to drain for about 30 minutes, or wrap it in a clean tea towel and gently squeeze it to remove the excess liquid. Put the zucchini in a large mixing bowl.
Heat a large skillet and add the sausage. Cook until the sausage starts to brown, stirring to break it up. Pour off all but about 3 tablespoons grease. Add the onions and cook until soft, about 5 minutes.
Stir in the garlic and cook 1 more minute. Combine the sausage and onions with the zucchini.
Stir in the cream, bread crumbs, eggs, cheese, and the pecans. Add salt, pepper, and hot sauce to taste. Pour the mixture into the baking dish. The casserole may be refrigerated at this point for up to 2 days or frozen.
For the topping, combine the butter, bread crumbs, and the pecans. Sprinkle evenly over the casserole. Bake, uncovered, about 30 minutes.
Sprinkle the top with the 1/2 cup cheese and return to the oven just until the cheese is melted and lightly browned.