Your job will consist mostly of cleaning exhibits, holdings, stalls, and dishes. If you are getting into this field to 'pet or play with the animals all day' you are in the wrong place. You work weekends, holidays, and long hours for not much pay. There isn't much room for advancement and it is a very physical job. Upper management doesn't care about the little people below them and you always must keep in mind that fund raising and donors will take precedence over anything else...the zoo has to bring in money to survive!
That being said: it can be a wonderful place to work. If the small percentage of time you get to train, observe, and otherwise interact with the animals in your care is worth the rest, then you will be happy. It takes a special kind of person to be a zookeeper! Make sure you volunteer first to get an idea of exactly what the job is all about.