Help with host.create via API using bash and curl

[ledgewatcher]

Hi I have recently implemented a basic Zabbix installation at my company as a POC and they now wish me to take it further. I found an old v3 script I have used in the past and expected it to work with some revision.

I want automate creating new hosts in Zabbix, initially to only assign them a template and hostgroup. I have hit an issue I cannot seem to work. I have tried escaping double quotes which I expected to be the issue.
I hope someone in the community would be able to assist.

I am using a bash script with curl to post the data request.
Curl is RHEL 7 v7.29. I have stripped out all variables whilst trying to debug.

The error that is always returned from the API using host.create is ;

"jsonrpc":"2.0","error":{"code":-32700,"message":"Parse error","data":"Invalid JSON. An error occurred on the server while parsing the JSON text."},"id":null}

I am able to use a variation of the code to gain an auth token or create hostgroups, so the API is working, but host.create does not.
The auth token I am using to debug is temporarily for the zabbix admin user, to be sure it's not a permission issue (sub'd in output for 123456)
I have also tried placing the JSON in a file and using the curl --data @file option with the same result.

create=$(/usr/bin/curl -s -X POST -H 'Content-Type:application/json' http://zabbix/zabbix/api_jsonrpc.php -d " {
     \"jsonrpc\": \"2.0\",
     \"method\": \"host.create\",
     \"params\": {
     \"host\": \"testlinux\",
     \"interfaces\": [
       {
        \"type\": 1,
        \"main\": 1,
        \"useip\": 1,
        \"ip\": \"172.20.1.1\",
        \"dns\": \"\",
        \"port\": \"10050\"
        }
        ],
        \"groups\": [
       { \"groupid\": \"49\" }
       ],
        \"templates\": [
       { \"templateid\": \"10081\" }
       ],
       },
        \"auth\": \"123456\",
        \"id\": 1
       }"
       )

echo $create

Thanks in advance.