BitcoinZ is a ZEC fork.  It is a community coin like BTC started. 

BitcoinZ has the same functionality as ZEC.  Even the version numbers are the same.  The difference is with mining and the fact their is a limit of 21 Billion Coins for BitcoinZ instead of 21 million for ZEC.  This does not include the wallet differences.

The community and developers decided not to make any changes to ZEC when forking this coin.  A great decision because ZEC and ZEN are the two best coins.  And keeping the functionality the same as ZEC means it can't be screwed up. 

Think of this as a practical application of ZEC.  There are enough coins for everyone.  Anyone can own numerous BitcoinZ coins.  Not so with ZEC - most can only own fractions.  This means that BitcoinZ can used as a means of exchange.  This coin can used as currency. 

Buying something with Bitcoins or ZEC is like trying to buy a pizza with a gold bar and a hacksaw.  Buying something with BitcoinZ is like using cash anywhere in the world with an optional privacy feature - ZK Snarks (Zero Knowledge Algorithm).

This coin has great potential for any developer to build a wrapper around the coin and for actual currency utilization.