Creating user privileges
A freshly installed ZFS volume comes with restrictive user privileges. To use it normally, you will have to create new user privileges.
Click at the icon of your mounted ZFS pool on your desktop, select in the menu bar File > Get Info.
Click at the little lock icon at the bottom, type in an admin username and password.
Click at the Plus icon at the bottom on the left.
Add a your own user name or all administrators with read and write privileges.
Try to copy some file to your pool.