Greece requested a new three-year bailout from its skeptical eurozone creditors and pledged some economic overhauls on Wednesday, but the euphoria some Greeks felt after Sunday’s “no” vote on the last deal was fading fast.

Whether European leaders accept the Greek government’s application for more emergency loans at a crisis summit Sunday still depends on Prime Minister Alexis Tsipras making a drastic turnaround on pension cuts, tax increases and other austerity measures after five months of often-acrimonious negotiations....