I agree with the other comments here. If your email system is blocking anything over 25MB, there's a good chance security settings would also block ZIP files anyway.

In practical applications, the attachment limit is actually less than 25MB because headers and other things get added that will increase the size of the email.

In my experience I've had to limit the total file attachments to 20MB or less to ensure I don't get any kickback from our expected recipients.

Honestly, the folder link is really the ideal way to handle this because you shouldn't be sending anything that large via email, but if they can't be sold on that, then the only option would be break it into smaller chunks for each email, and that is going to get very complicated.

When you set attachments for a Workflow email activity, you either need to send everything, or specifically attach every item in the configuration so it can't be that dynamic without SDK Scripts.

You'd likely have to do something like loop through each file and keep track of the file sizes, move them into subfolders until you hit your limit and start a new subfolder.

Then, iterate through your subfolders and attach everything from the subfolder in each email you send.