Complex sentence: Donald Leon "Don" Blankenship (born March 14,1950) was both Chairman and CEO of the Massey Energy Company--the sixth largest coal company (by 2008 production) in the United States--from 2000 until his retirement in 2010.
Split into simpler sentences: Donald Leon "Don" Blankenship (born March 14,1950) is retired American business executive. He was Chairman and CEO of the Massey Energy Company--the sixth largest coal company (by 2008 production) in the United States--from 2000 until his retirement in 2010.