Complex sentence: Houghton Mifflin acquired Harcourt in 2007, and assumed the Harcourt name in the Houghton Mifflin name to form Houghton Mifflin Harcourt.
Split into simpler sentences: Houghton Mifflin acquired Harcourt in 2007. It incorporated the Harcourt name to form Houghton Mifflin Harcourt.