Euro zone leaders will fight to the finish to keep near-bankrupt Greece in the euro zone on Sunday after the European Union’s chairman canceled a planned summit of all 28 EU leaders that would have been needed in case of a “Grexit”. In return, leftist Prime Minister Alexis Tsipras will be required to enact key legislation in parliament on Monday to start restoring the broken trust of his partners in the 19-nation currency union to win a third bailout, ministers said.