Complex sentence: The Main Valley was closed due to its age, being incapable of holding animals safely, and the Reptile House was closed because since it wasn't inside the zoo, it needed a separate entrance fee and led to occasional robbiers.
Split into simpler sentences: The Main Valley was closed as well due to its age, being incapable of holding animals safely. Its Reptile House was also closed because since it wasn't inside the zoo, it needed a separate entrance fee which also led to occasional robbiers.