A zookeeper takes care of animals in a zoo. I imagine a zookeeper job can be as mundane, as it can be rewarding, as you could be preparing feed or delivering babies.
Click here for the website to the San Diego Zoo for a description of an animal keeper.
A zoologist studies and researches about animals. Zoology is a broad field of study. There are many types of animals from protozoa to gorillas; sea slugs to dolphins and many fields to study from physiology to taxonomy, biochemistry to sociobiology. You can get paid to research, teach or care for animals. Zoos definitely hire zoologists.
Click here for the career description of a zoologist.
There are many careers available to a zoology major - zookeeper, zoologist, naturalist, warden, teacher, biologist. I majored in zoology with a primary emphasis in entomology. I was lucky enough to get a job that utilizes my education.
Sounds like you want to become a zoologist with a specialty in large cats. You will likely have to become a PhD who works for a university, zoo, the government, a preserve or park. Are you prepared to work in Africa, as large cats are primarily found there? Or you could become a technician who helps with the grunt work or data collection (PhD's generally not required). Or you could become an administrator or zoologist who helps works in a preserve or park.