If bitcoin dies , Zcash will up and running the show. It's just a matter of switching to an alt coin.
For sure everyone will have to migrate to another coin to continue but it is probably hard to believe if bitcoin really dies, what about the people holding thousands of bitcoins in their wallets and what about the ones running exchanges and other websites with bitcoins? They would surely cry all day and then move towards something else.
Bitcoin will be the last cybercoin to die, so many people have interests in it and will support it the best they can. Zcash is a joke, it is like any other altcoin, it will die before bitcoin for sure, without any doubt.