If they get large I make stuffed zucchini. I stuff it with cooked rice mixed with cooked Italian sausage (I prefer hot) chopped onion and peppers (also cooked) and the guts of the zucchini if it isn't too seedy yet. If it is seedy then I give the seeds to my chickens and add only a bit of the scraped out zucchini meat to the mix. For 2 extra large zucchini I will use 2 cups cooked rice, 1lb sausage meat, one medium size finely chopped onion and a large bell pepper chopped. I also mix in fresh herbs like basil and thyme. Salt and pepper to taste.
I sometimes put in a chopped tomato. Mix all this up, fill up the raw zucchini "boats" and bake it for about 40 minutes in a 350 oven. This is good all on its own but you can add shredded cheese to melt on top at the end. I prefer it without the cheese. (less calories!)
Another favorite way is grilling. I will cut thick slices of zucchini on the diagonal to increase the surface space. I mix some olive oil, lemon juice, clove of crushed garlic and fresh basil finely chopped. I line the slices up on a cookie sheet and brush them with the seasoned oil then flip brush the other side and cook them on a hot grill. Very yummy.
Zoodles are all the rage now. And of course there is zucchini bread.