Complex sentence: The line was extended from Nerima to Shinjuku on December 19,1997, and later to from Shinjuku to Kokuritsu-Kyogijo on April 20,2000.
Split into simpler sentences: The line was extended from Nerima to Shinjuku on December 19,1997. And the line was also extended from Shinjuku to Kokuritsu-Kyogijo on April 20,2000.