Sri Lanka's Upul Tharanga and Tillakaratne Dilshan recorded the fourth-highest stand for any wicket in a one-day international on Thursday, scoring 282 before they were parted.
Tharanga was eventually out for 133, caught by Elton Chigumbura off Chris Mpofu in the 45th over and Dilshan, on 144, followed shortly afterwards, caught by Tinashe Panyangara off Prosper Utseya.
The partnership was just four runs short of a stand of 286 for the first wicket between Tharanga and Sanath Jayasuriya at Leeds in 2006.
The duo sailed past the previous World Cup best for the first wicket of 194 made by Pakistan's Saeed Anwar and Wajahatullah Wasti against New Zealand in Manchester in 1999.
"Dilshan played really well. He got a magnificent start and got momentum so I played around him," said Tharanga.
Sri Lanka were put into bat by Zimbabwe in a game where victory for the co-hosts will guarantee a quarter-final place.