Complex sentence: Had he been elected, the then 50 year old Shashi Tharoor would have been the second-youngest Secretary-General to be appointed to the post, the first being Dag Hammarskjöld who was appointed at the age of 46 years.
Split into simpler sentences: Had he been elected, the then 50 year old Shashi Tharoor would have been the second-youngest Secretary-General to be appointed to the post. The first being Dag Hammarskjöld who was appointed at the age of 46 years.