Many monitoring tools have feature to activate/deactivate nodes monitoring remotly.
For instance, when database backup is launched, database is offline during backup. As we don't know exactly at what time the backup is started and finished (cause this is usually manage by a tool scheduler), it's difficult to set an appropriate maintenance period.
Other monitoring tools allow to send kind of trap/notification to inform tool to suspend monitoring send a new trap/notification to inform that backup is finished and tool can now reactivate the monitoring. I don't see that feature in zabbix. May be using zabbix_sender/zabbix trapper could be usefull to have such feature.