Complex sentence: Moscow Oblast gubernatorial election of 2013 was held on September 8,2013 as part of regional Election Day, which consist elections in 9 other Oblasts and mayoral election in the federal city of Moscow.
Split into simpler sentences: Moscow Oblast gubernatorial election of 2013 was held on September 8,2013 as part of the regional elections, where 9 other oblasts held elections. It was also the same day as the mayoral election in the federal city of Moscow.