Hello.

For big products with a lot of linked services within zabbix - better to have one report for SLA. 

It is possible to add excluded downtimes to align with real planned works - this is OK.

But it is impossible to guarantee that 100% of issues will be reflected by monitoring system. Some incidents will be raised by the business clients. 

As I know - it is impossible to create lets say "synthetic problem" related to the service in the past to correct SLI and align real condition.

It could be useful to improve SLA report trust.

Of course activity like this should be done with full logging and with mandatory descriptions.