it would be easier if you send us a sample msg from that node to see its structure but luckily there is an example of the node's page

the expression $moment().tz($$.location.timezone).format("z Z")
in a Change node
will produce this format CST -06:00
test Flow:
[{"id":"3bbd3677c8b9707f","type":"inject","z":"a479605cda9a7cfd","name":"ip node","props":[{"p":"payload"},{"p":"location.timezone","v":"America/Chicago","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"\"123.123.123.123\"","payloadType":"str","x":250,"y":900,"wires":[["0b7720798a9f4ec7","4c6ca52050b3b727"]]},{"id":"0b7720798a9f4ec7","type":"change","z":"a479605cda9a7cfd","name":"","rules":[{"t":"set","p":"payload","pt":"msg","to":"$moment().tz($$.location.timezone).format(\"z Z\")","tot":"jsonata"}],"action":"","property":"","from":"","to":"","reg":false,"x":520,"y":900,"wires":[["1b814eaabdf51194"]]},{"id":"1b814eaabdf51194","type":"debug","z":"a479605cda9a7cfd","name":"debug 26","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":720,"y":900,"wires":[]},{"id":"4c6ca52050b3b727","type":"debug","z":"a479605cda9a7cfd","name":"debug 27","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","targetType":"full","statusVal":"","statusType":"auto","x":420,"y":820,"wires":[]}]