Do I always need to have an empty Inbox (Inbox Zero)?

No. The goal is to process quickly and avoid accumulating emails.

How do I do this in Outlook?

1. Quickly archive
   • • Select email → Backspace key (Archive).
     • Or Home → Archive.
2. Schedule for later
   • • Right-click on the email → Follow up → Add Reminder.
3. Delete
   • • Select email → Delete key.