Of course they're professionals, but modern Zoos are there for entertainment first. The conservation part is not priority anymore. If we need them for conservation then let's focus on that, no need to have thousands of people visiting.
And no need to spend lots of money each day to feed the animals. Just put the zebras and lions in the same recint and watch the good old PETA-approved nature in action. You obtain super-happy lions (except those kicked in the head with an open fracture maybe).
