Simplify the following text for a Grade 7 native English-speaking person.
Original: Steglitz-Zehlendorf is the sixth borough of Berlin , formed in Berlin 's 2001 administrative reform by merging the former boroughs of Steglitz and Zehlendorf .
Simplified: Steglitz-Zehlendorf is a borough of Berlin . It was formed in 2001 when the former boroughs of Steglitz and Zehlendorf were joined together .