With it use BTC or have a new money supply, or both? Will it be launched as a Bitcoin sidechain, or are there any plans to make it one after launch?
The original zerocash team approached the bitcoin developers over a year ago asking to integrate some of their ideas into the bitcoin blockchain and were turned down entirely. So they went underground and developed zcash.
Zcash still seems to share quite a bit in common with bitcoin, however. For example, they are sticking with the 21,000,000 coin market cap.