Complex sentence: In 1921, the school changed its name to National Southeast University and became the second national university in China, and was renamed to National Central University in 1927 and soon became the nation's flagship university.
Split into simpler sentences: In 1921, the school changed its name to National Southeast University and became the second national university in China. Later SEU was renamed to National Central University in 1927 and soon became the nation's flagship university.