Complex sentence: Matteo Renzi (born 11 January 1975) is an Italian politician who has been the Prime Minister of Italy since 22 February 2014 and the Secretary of the Democratic Party since the 15 December 2013.
Split into simpler sentences: Matteo Renzi (born 11 January 1975) is an Italian politician who has been the Prime Minister of Italy since 2014 and the Secretary of the Democratic Party since the 2013. Renzi is also the Secretary of the Democratic Party since 15 December 2013.