Sending SNMP traps to upstream systems is not well documented but can also be done by configuring a Notifications mechanism when Zabbix detects an event.
a. Configure a new media type (Adminstration, Media types tab). Media types are one of the following (E-mail, SMS, Jabber, Ez Texting & Custom alertscripts). Custom script media type can define a script which will invoke the 3rd party snmptrap binary which is included in the net-snmp-utils package. The script you write needs to be placed on the zabbix server in: /usr/lib/zabbix/alertscripts
b. Step 2 requires linking the media type with an Action delivery mechanism (Configuration, Action). You can configure what actions to report to each media type and what condition will trigger sending a message. The Actions allows sending both a Trigger message and a Recovery/Clear message. The default message provides the following fields but I believe we could tailor these to match our current MCAS SNMP events as well.

Trigger: {TRIGGER.NAME}
Trigger status: {TRIGGER.STATUS}
Trigger severity: {TRIGGER.SEVERITY}
Trigger URL: {TRIGGER.URL}

Item values:

1. {ITEM.NAME1} ({HOST.NAME1}:

But here my question is how do I create a custom script in order to send out snmptraps for these triggers? Is it possible to define a general operation which will be applicable for all the triggers? (I created multiple triggers and defined an action also a custom script to the media type.)

But currently there is no capability in zabbix to forward SNMP traps to any external system with the mapping of these triggers not there are any clear documentation available on SNMP trap forwarding.