Hi @EllieH, welcome to the Community!
It’s not possible to create a Zap that would do that using the Mailchimp integration as it is, we do have a feature request open to add a trigger for bounced emails and I’ve added you as an interested user on that. I don’t have an ETA of when/if that will be added, but we’ll update this thread and send you an email if it is.
I took a look at the MailChip API (the bit code that lets other apps send information to/from Mailchimp) and although it’s possible to get a list of member activity (ie you can see all members, which would show those who have been unsubscribed due to bounces) it doesn’t look like there’s a way to ask MailChimp to send a notification/information each time a bounce happens. That means that it would be very difficult if not impossible for you to do this yourself using a webhooks step.
One way that you could automate some of this process would be to use a Transfer. If you can export the list of bounces from Mailchimp into Google sheet, you could then automatically update the relevant information in Maximiser CRM.
I hope that helps, please let us know if you have any questions!