Short answer
HubSpot's KB: turn on Sync webinar data to sync registrants and attendees. The integration only accepts the required First name, Last name and Email fields in the Zoom registration link. Zoom Events aren't supported, and Total number of Zoom Webinars attended doesn't increase for the same recurring webinar.
1. Marketing events
Marketing events in my demo portal.

2. Workflows
HubSpot's KB also covers adding contacts to Zoom webinars with workflows.