Hello @Raj.Mashruwala ,
At this time, there isn't really anything in-product you can do beyond unsubscribing the bad contacts. However, unsubscribed and awaiting confirmation contacts can still technically sign up for events, if they have a link to the registration form (from it being shared on social media, your website etc.). It's also entirely possible for these bad contacts to re-subscribe themselves using a sign up form, or to subscribe with a different email address.
If you're noticing it's the same email addresses being used for registration and Zoom link access, there is a convoluted method you could try. It would involve you immediately, manually registering their email addresses each time you set up a new workshop event registration. That way, at the very least they can't use those emails to sign themselves up. However, if you end up sending an email that targets specifically registrants, then they'd still end up receiving it and presumably the link to your Zoom.
If we knew more about the source of these contacts, and how they're adding themselves to be able to access your Zoom links, we may be able to explore more options on our end. Knowing the specific bad contacts' email addresses would be the start. The Global Block List would be the nuclear option, but since the request to be added wouldn't be coming from the customer, we'd need some evidence of abuse. A video or something else that shows how they keep messing with your workshops, keep signing themselves back up, etc. It would likely be worth calling our Review / Compliance team to see what further insight they can offer, and what the best option would be to prevent these bad contacts from continuing to harass you.
With all that said, it may be worth reaching out to Zoom's support to see if they have any further insight. It's possible they may have ways to prevent certain IPs, or other specific elements of these bad actors, from accessing your workshops.