Systemd by Zabbix agent 2 - see setup instructions for Zabbix agent 2 templates.
You can get these templates:
In Configuration → Templates in new installations;
If you are upgrading from previous versions, you can download new templates from Zabbix Git repository or find them in the templates directory of the downloaded latest Zabbix version. Then, while in Configuration → Templates you can import them manually into Zabbix.