Which zone type allows traffic between zones in different virtual systems (VSYS), without the traffic...

The Transient zone type is used to allow traffic between zones in different virtual systems (VSYS) on a Palo Alto Networks firewall without the traffic leaving the firewall. It provides a way for virtual systems to communicate with each other by acting as a temporary or intermediary zone. Traffic can pass through the firewall between the virtual systems without requiring physical interfaces or leaving the device.