We use Zabbix with PagerDuty and have enabled Urgencies (https://support.pagerduty.com/hc/en-us/articles/207756948-How-do-I-enable-Urgencies-).

We have defined two different actions for High and Low urgency escalations, the conditions are exactly the same the only thing that differs is the different different Trigger severity rules.

When Trigger severity = High , escalated to the High Urgency service.
When Trigger severity = Average or Warning , escalate to Low Urgency service.

Unfortunately it seems that for every High severity we also get the same alert escalated to Low Severity which is very annoying because we get paged twice in PagerDuty.