Complex sentence: In the first round of the doubles competition, partnering with her sister Venus they lost to Czech duo Lucie Šafářová and Barbora Strýcová, ending their career record of 15--0 dating back to the 2008 Olympics.
Split into simpler sentences: In the first round of the doubles competition, partnering with her sister Venus. They lost to Czech duo Lucie Šafářová and Barbora Strýcová, ending their career record of 15--0 dated back in the 2008 Olympics.