Are you sure they use html email?
Can you really bother them by sending an attachment that only works through Microsoft OneDrive, Google Drive, or Dropbox?
If you embed links and attachments within the email, do you know what will happen to their computer if they click on a link?
Do Zoom hotlinks – where you can’t see the Zoom meeting number – cause difficulty when someone actively uses 4 or 5 Zoom accounts for all their various gigs and jobs?
Can you assume they are able to register for a event and then sucessfully recieve the email with the actual Zoom link later? And accomplish this in another time zone at an odd hour on their phone?
Do they have a disability they don’t want you to know about and your fancy stationary html email is really just difficult to read?
Do you really need any graphics whatsoever in any email, ever?