Ok so I looked at the Zosi Smart app and its similar to how our Amcrest cameras are. When you go to Add Device on the app and then select IP Camera you then select Camera C199 (thats your camera model). It wants to scan a QR code. From what I can tell its on the bottom of the Camera. Our Amcrest ones you can look under the Network settings and find the QR but I don't know if your camera has something like that.
As long as the camera can connect to the Internet and register itself with the Zosi cloud services you should be able to view it anywhere without setting up port forwarding. The camera probably registers itself using its Serial Number and then your app needs the QR code that contains the camera Serial Number to connect to it.
When you are looking at the settings are you using the app on your phone? Have you tried going to a PC on the same LAN and typing in the IP in a browser?
If that doesn't work you may need to use a different IP camera viewing app that allows you to view a camera by IP. Then I would try doing a 1:Many NAT
Your Public IP - TCP - (Pick a public port) 1234 - LAN IP 192.168.128.73 - Local Port 37777 (37777 is a typical TCP camera video streaming port) - Allowed IPs Any
Your Public IP - UDP - (Pick a public port) 1235 - LAN IP 192.168.128.73 - Local Port 37778 (37778 is a typical UDP camera data streaming port) - Allowed IPs Any