Both Zerocoin and Zerocash are abject trash until they demonstrate that the necessary key can be created in a trustless manner. I doubt that is possible. Even if it is, there will always be a degree of doubt. The consequences of such a key being retained and misused would be disastrous. Why even take the risk when there are other solutions without this issue? Perhaps zero knowledge proofs will have some applications, but a cryptocurrency is not one of them.