Steps to reproduce:
Install the Zabbix agent with a comma-delimited string for the HOSTNAME parameter.

msiexec /l*v log.txt /i zabbix_agent2-6.2.3-windows-amd64-openssl.msi /qn SERVER=127.0.0.1 HOSTNAME=host1.example.com,host2.example.com 

Result:
See log file.

Expected:

1. 1. 1. Option: Hostname
2.    List of comma delimited unique, case sensitive hostnames.
3.    Required for active checks and must match hostnames as configured on the server.
4.    Value is acquired from HostnameItem if undefined.
   #
5. Mandatory: no
6. Default:
7. Hostname=

Hostname=host1.example.com,host2.example.com