On Windows when LogFile option is not set Zabbix agent is supposed to write log messages to Windows event log. But the

		ReportEvent(
			system_log_handle,
			wType,
			0,
			MSG_ZABBIX_MESSAGE,
			NULL,
			sizeof(*strings)-1,
			0,
			strings,
			NULL);

fails with ERROR_INVALID_PARAMETER because the wNumStrings parameter is calculated incorrectly. It should be sizeof(strings) / sizeof(*strings) rather than sizeof(*strings)-1

Another problem is that agent always tries to use "Zabbix Agent" as event source event if multiple-agents startup option was specified.