I do not use Zoho for file storage and thus I cannot tell you much about that - you'll have to speak to Zoho yourself and/or look at their website information and third-party reviews - however the email service is exceptionally good in my experience (you can add verification features when using a custom domain like SPF records as well).
Apparently, Zoho have Encryption At Rest (EAR) support for content stored:
https://help.zoho.com/portal/community/topic/server-side-at-rest-file-encryption
Secure cloud storage for team files | Zoho WorkDrive
Encryption Process in Zoho CRM
If there's one thing I really like about Zoho, it's the security settings for account authorisation. They support the traditional 2-Factor Authentication (like with SMS verification) but they have other offerings included for Multi-Factor Authentication.
If you're only concerned about the data storage capacity, why not consider a combination of MEGA, Google Drive, and Dropbox? All of them offer free plans. As long as you can manage your accounts for them, then you can get an extremely large data storage capacity on the cloud between them all for "free".
Dropbox also have ways to get data storage extensions through invite referrals.