A server-admin in the USERS-zone requires SSH-access to all possible servers in all current and...

Create a custom-service-object called SERVICE-SSH for destination-port-TCP-22. Create a security-rule between zone USERS and OUTSIDE to allow traffic from any source IP-address to any destination IP-address for SERVICE-SSH

Create a security-rule that allows traffic from zone USERS to OUTSIDE to allow traffic from any source IP-address to any destination IP-address for application SSH

In addition to option a, a custom-service-object called SERVICE-SSH-RETURN that contains source-port-TCP-22 should be created. A second security-rule is required that allows traffic from zone OUTSIDE to USERS for SERVICE-SSH-RETURN for any source-IP-address to any destination-Ip-address

In addition to option c, an additional rule from zone OUTSIDE to USERS for application SSH from any source-IP-address to any destination-IP-address is required to allow the return-traffic from the SSH-servers to reach the server-admin