just in case someone comes around this question using search engines as I just did.
Zabbix offers since v3.0.0beta1 the "-f" option to run in foreground (https://support.zabbix.com/browse/ZBXNEXT-611)
As you can see below, we start the process using the absolute path to binary (we compiled it from sources), providing our configuration-file using the "-c" switch and absolute path to the configuration file. And then the mentioned "-f" switch to run the process in foreground.
The supervisord configuration file we use looks like:
command=/opt/application/zabbix-server/3.2.7/zabbix_server -c /opt/application/zabbix-server/3.2.7/zabbix-server.conf -f
Please note that we configured in the zabbix-server.conf
All the best