Most of available mysql monitoring template uses one user parameter per item. Therefore to collect values for n items, they will run n mysql command (or same command n times and get extract desired information from result). This monitoring template instead get complete result in one item as json content and then uses dependent items to create multiple items on zabbix server.

More information available at https://tachniki.blogspot.com/2019/03/mysql-and-mysql-slave-monitoring-zabbix.html. 

Template available at https://github.com/nitzien/zabbix-misc/tree/master/templates/mysql