Bit of a strange title and request but here goes.

I would like to update my ipv4 WAN ip address and also the ipv6 ip but this from a particular PC desktop. Currently I run a curl command from my router

curl -k --silent "https://api.dynu.com/nic/update?hostname=xxxxx.dynu.net&password=password"

and then use the client app on the particular desktop to update just the ipv6.

I would like to do his all in one place but if in the client app I also enable the option to update the ipv4 then it uses the local ipv4 of the desktop and not the WAN and if I select the WAN then when it updates the ipv6 it uses the ipv6 of the WAN?

What programming language would you be trying to do this with?

Also how do you envision making the the edits to switch functionality that you describe? (e.g. raw code edit, cli, gui)?