Complex sentence: In 2007, at the age of 23, Zuckerberg became a billionaire as a result of Facebook and the number of Facebook users worldwide reached a total of one billion in 2012.
Split into simpler sentences: In 2007, at the age of 23, Zuckerberg became a billionaire as a result of Facebook's success. The number of Facebook users worldwide reached a total of one billion in 2012.