An email message translated with Unbabel can reach any cc'ed or bcc'ed recipients in a ZD ticket. However, you need to take into account some limitations.
Zendesk only updates the recipients of a ticket if you add/removed them with the comment box is set to public reply mode. Even if you change the recipients and switch to private note before updating the ticket, you lose all changes.
Because Unbabel relies on a private note being posted to request a translation, if you want to include new recipients or remove them in the next reply, you need to make sure you make these changes and update the ticket as a public reply (suggestion: change the recipients and do a blank update) and only then use Unbabel to translate the message.