Hey @HChirra,
If you have finished the Oauth flow for webinar Webhook App on zoom config page from the following link, after the webinar ends, it will synchronize webinar details including actual start/end time, participant count immediately. After 5 minutes, the attendees info will be synchronized to salesforce.
If the attendees aren’t synchronized to salesforce successfully, you can also click the manual sync button on the Zoom webinar detail page to synchronize the info.
Thanks,
Tommy