If unfortunately the password for Zabbix has been lost. How can you change this

You have to login to database CLI and connect to zabbix database.

sudo -u postgres psql
\c zabbix

Or you can do like this

sudo -u postgres psql zabbix

You have to change some user’s password to a new password

update users set passwd=md5('superduperpassword') where alias='Admin';

If you want to be sure that everything worked out, you need to do it (the hash must be different)

select * from users;

No need to restart zabbix