I paid extra (on top of regular admission) to part...

I paid extra (on top of regular admission) to participate in the Koalas and Friends Behind the Scenes Tour. This tour takes place before the zoo opens.
We had a great tour guide who happened to be a school teacher with a Master's degree. She had worked at the zoo during her summer breaks. After teaching in the classroom, she realized that she missed helping with animal conservation. So, she came back to the zoo full time.
Our zoo guide was definitely lively and knowledgeable, but also patient and kind with young and old alike. She took time to answer all our questions.
We rode around the zoo in an extended golf cart which made it super easy to maneuver the 100 acres. We stopped at key points to look at the animals and learn about them.
My 86 year old mother and my favorite part was getting up close to see and photograph the koalas. (Patrons aren't allowed to touch the koalas as it is a regulation in the USA.) We got to learn a great deal about them. It was very enjoyable.
Afterwards, we boarded the regular bus that drove around the zoo.
I've been to many zoos including some in Europe. I highly recommend this zoo and encourage you to take one of the behind the scenes tours. You won't regret it.