1Cut zucchini in half lengthwise and remove seeds. Microwave, in batches, in a 11 x 7 inch glass dish at HIGH 5-7 minutes or until tender. Scoop out pulp, keeping shells intact; reserve pulp. Sprinkle shells with salt.
2Stir together reserved pulp, cheese and next 4 ingredients. Fill shells with pulp mixture; place in a 13 x 9 inch baking dish. Sprinkle evenly with breadcrumbs; drizzle with butter.