• Google: Gmail, Calendar and Contacts.
• Microsoft: Outlook, Calendar and Contacts.
• Calendly: your scheduling links.

Connect them during first-run setup or later in Settings, Connections.

Settings, Connections has a search for everything else you can connect. Some services need extra setup or approval before they work, and Settings tells you which.

• Zero reads your recent mail, calendar and contacts into your own private data store. What it can read depends on the permissions you grant and what the service makes available.
• Smart Manager doesn't become your email host. Your mail stays with your provider.
• Actions with outside effects, such as sending a message or submitting a form, ask for your approval first.
• During a trial, Smart Manager reads up to 500 email threads from the last 90 days, newest first.

• Settings, Connections: disconnect to stop syncing. What was already brought in stays until you delete it.
• Settings, Privacy, Imported data: choose Disconnect and delete to also delete the email, calendar events, contacts and messages that account brought in. Its documents leave your library and search; the stored files are removed when you delete your account. Facts learned from it stay in Memory, where you can review and forget them.
• You can also revoke access from your provider, for example in Google's third-party access settings.
• YouTube has its own steps: see Manage YouTube data.