What data is accessed when sending phishing email by replying to existing email with zip file attachment

Emails were sent from a professional to two different addresses. They are both a reply to previous emails sent to the professional. They each contain a short sentence, in one case unfinished sentence, inviting the recipient to click on a Zip file attachment. The attachment is a malicious Excel file.

My question is with regard of the data accessed. Obviously, the data on the email they replied on has been accessed. What about the rest of the data on the mailbox? What exploitation is done by this data collected? The phishing strategy looks similar to the EPIC Machengo spotted by Nviso.