Nifi process group monitoring

[#1]

I created new Reporting task in Nifi with process group ID to monitor specific Nifi process group.
I can see data from this Reporting task in Grafana, but I am unable to get this metric via some API interface to pass it to the Zabbix dashboard for alerting purposes. I have tried the following:

$ curl -u xxxx:******** -H 'X-Requested-By: ambari' http://myhost:6188/ws/v1/timeline/metrics?metricNames=nifi.BytesWrittenLast5Minutes.0373e5ac-51dc-33...
[1] 30260
$ {"metrics":[]}
[1]+ Done curl -u xxxx:******** -H 'X-Requested-By: ambari' http://myhost:6188/ws/v1/timeline/metrics?metricNames=nifi.BytesWrittenLast5Minutes.0373e5ac-51dc-33...
$

and

$ curl -u xxxx:******** -H 'X-Requested-By: ambari' http://myhost:6188/ws/v1/timeline/metrics?metricNames=AMBARI_METRICS.nifi.BytesWrittenLast5Minutes.0...
[1] 1866
$ {"metrics":[]}
[1]+ Done curl -u xxxx:******** -H 'X-Requested-By: ambari' http://myhost:6188/ws/v1/timeline/metrics?metricNames=AMBARI_METRICS.nifi.BytesWrittenLast5Minutes.0...
$

But either of these are correct responses.

What I am missing or doing wrong?

[#2]

Ambari version is 2.5.2.0, HDP version is 2.6.1.0 and Nifi version is 1.2.0 (I have HDF integrated to the Ambari).

[#3]

you can add a reporting task for zabbix

https://github.com/dbist/workshops/tree/master/nifi/templates/zabbix

https://pierrevillard.com/2017/05/11/monitoring-nifi-introduction/

[#4]

Thank you Timothy especially for the Zabbix example!

Unfortunately I am looking for different kind of solution here.
So my question remains. How to get Ambari metrics values via curl?