Complex sentence: The Vatican City, even though not a member of the European Union, it has joined the Eurozone in 2002 since it has a special agreement with the EU that allows this microstate to mint a limited number of euro coins.
Split into simpler sentences: The Vatican City, even though not a member of the European Union, became a member of the Eurozone. Since 2002 it has had a special agreement with the EU that allows this microstate to mint a limited number of euro coins.