They surpassed the previous record of 263-5, set by Royal Challengers Bangalore in 2013
Azhar, 30, played the last of his 14 one-day internationals over two years ago but is a regular in the Test side batting at number three.
"In view of his character, leadership and team spirit, the decision has been made to make Azhar new ODI captain," Pakistan Cricket Board chairman Shahryar Khan told reporters in Lahore on Monday.
Pakistan lost to hosts Australia by six wickets in the World Cup quarter-finals 10 days ago.