Here's one my grandmother used to make, and we still like it:

The amount of ingredients doesn't really matter, just use your common sense in terms of the amount you need (or the amount of zucchini you want to get rid of!)

4 medium zucchini or other summer squash
1/2 cup crushed crackers, either saltine type or ritz type
1 cup shredded cheddar cheese
1/2 cup undiluted canned milk

Dice squash and parboil just a a few minutes, in salted water if you prefer. In a buttered casserole put a layer of well-drained squash, layer of grated cheddar cheese, and a layer of crushed cracker crumbs. End the layers with cheese and crumbs.

Pour undiluted canned milk over all. Cover and "bake until ready" - in other words, at 325 - 375 for 30-40 minutes.