Simplify the following text for a Grade 6 native English-speaking person.
Original: Thomas DÃ rflein ( 13 October 1963 â `` 22 September 2008 ) was a German zookeeper at the Berlin Zoological Garden for 26 years .
Simplified: Thomas DÃ rflein ( 13 October 1963 â `` 22 September 2008 ) was a German zookeeper at the Berlin Zoo for 26 years .