It starts very well, with well-made visuals of zombie attacks, and a nice play on 'rules to survive'. It sadly gets messed when it's clear the writers did not know where to run with the story, and made even worse by the sisters, who serve only to annoy, especially the older one. Her failed attempt at sex appeal and sass does not help.
I do however have to appreciate the moment where the Woody Harrelson character expresses great admiration for Bill Murray.