Check the NAT rule and then the Policy Control rules:

1) Create Service Objects for each External and Internal port you need ( one for 44443 and one for 9099 ) under Configuration-> Object -> Service.

2) Under your NAT rule use the new object ( for port 44443 ) as your External Port and then the other object ( for port 9099 ) as your internal port. Ensure the source/destination interfaces and source/destination address ranges are correct for your network as well. Save the NAT rule.

3) Now you want to check your Policy Rules under Configuration->Security Policy->Policy Control and/or create a rule there so that the firewall can handle the non standard port as it deals with the those inbound requests. Create a new rule from WAN as the source interface and your internal interface as your destination. External port will be the object you created for port 44443 and the internal port you would select the object you created for port 9099. Save the rule

These steps will completely allow the forwarding of all the traffic occurring on the external to your internal application.

If the ZYWALL or USG is interfering with the SSL of your custom web site in any way, it's because you've possibly configured the built-in ZYWALL SSL service to handle those ports, which is not what I believe you are trying to do.