Add a Issue Security Level. You probably will want that level to be the default issue security level.
Allow Group Custom Field Value of your Zone Field
You optionally may want to add the Project Roles Developers or Administrators additionally to let them have an overview over all issues.
Assign the Issue Security Scheme to the project where you want to restrict access. You may need to migrate existing security settings. Therefore you may want to have a legacy Issue Security Level in your scheme.