It is possible to set the sharenfs attribute in solaris zfs to share out to multiple subnets. The syntax must be correct though. Below is an example of the correct syntax for sharing a share in a pool to multiple subnets.
zfs set email@example.com/24,firstname.lastname@example.org/24' pool/share
The above command sets read and write to any address in the subnet of 192.168.50.xxx and 192.168.200.xxx. This is useful for restricting your zfs shares to only certain groups of hosts via nfs.