There is a Roy's which is excellent. It's a favorite of Obama's. Good seafood and sushi if you like that. Lots of good choices for steak. Chop house, Chicago Cut, Capital Grill. Have to get some Italian Beef. As PP said there is a Portillos close to you and an Al's which some say is the best. Chinatown also has some good options along with Greektown depending on your food preferences. BTW the Brookfield Zoo is not that hard to get to from downtown. The Metra has a stop in Hollywood which is just East of Brookfield. The zoo is within walking distance. However with your short stay it might suck up too much of your time.