The article explains if .zip compressed archives can be handled by the Attachment Isolation service in Email Threat Detection and Response
Email Security.cloud
The Attachment Isolation does not support the isolation of ZIP files.
By design, the service allows email recipients safely interact with attachments on the isolated platform. All document types are enabled by default, which means that all will be isolated. The attachment file types to isolate are listed in the Email Security.cloud portal under Dashboard > Services > Email Threat Detection and Response > Attachment Isolation Settings. Please see them below: