Normally, schedule deleting in Outlook sync with Dynamics 365.

However, in the below scenario, deletion doesn't sync with Dynamics 365.

Step 1. Delete schedule in Outlook

Step 2. Click [Synchronize with Dynamics 365] bottom before auto sync with dynamics 365

When this happen, we need to delete the [schedule] manually in Dynamics 365 for each.

It would be much better to be synchronized in this sceario.