It's a radically different approach. Zerocoin basically implemented a decenteralized 'mix' via a blind accumulator. Zerocash uses zero knoweldge proofs of exe

It's a radically different approach. Zerocoin basically implemented a decenteralized 'mix' via a blind accumulator. Zerocash uses zero knoweldge proofs of execution for general computation so that basically all properties of a coin can be completely blinded. In ZeroCoin, coins— all of equal denomination— go into a bag (one bag per denomination), and coins come out of the bag and you can't tell which was which (except, of course it can't come out until after it's gone in.). In Zerocash its more like everything is completely encrypted, even the values, the network knows that its all valid due to zero knoweldge proofs, but only the transaction participants know any of the details of the transactions at all. In some ways Zerocash is really the some of the most pedestrian applications of the ZK-SNARK technology, ... prepare to have your mind blown and go read some at http://www.scipr-lab.org/ http://www.scipr-lab.org/