"zk-SNARKs – the zero-knowledge proofs at the core of Zcash – require a parameter generation ceremony to take place for every statement that you wish to create proofs about. Although privacy is protected by zk-SNARKs unconditionally, if this ceremony is compromised it becomes possible to counterfeit Zcash. It is thus important for us to ensure these parameters are created securely."

- https://z.cash/blog/new-mpc-protocol.html

So I don't understand why anyone would not consider it possible for BitcoinZ to be counterfeited.