We went to the zoo on second Tuesday with the hopes that Lily, the baby elephant, would be viewable by the public. Looks like we just missed her by a couple of days. It is not every day you get to see a newborn elephant, if the zoo wasn’t on your itinerary I think you should add it in.
If you decide to go, I suggest taking the Max. My guess is parking will be pretty limited, plus you have to pay to park. If you take the Max you can show your ticket stub at the zoo ticket window for $1.50 off admission. To get there by Max take either the Red or Blue line heading west and get off at the Washington Park Station (only stop in the tunnel).by