zerotier-cli peers shows a list of nodes that your node knows about.
Nodes can not talk to each other unless they are joined and authorized on the same network.
The peers you are seeing could be:
ZeroTier Inc root servers.
These are hard-coded into the client
Network Controllers
A controller is a ZeroTier node. The first 10 digits of a Network ID is the controller’s address.
Nodes discovered from a previously joined and left network.
But again, they can’t talk to you or see your traffic unless they are on the same network. This applies to root and controllers too.