Thank you. For my Android I am going to try Zarchiever because I saw a positive report somewhere else on it.
It depends whether you want some inter-operability.  is "universal", not just for Excel files.  might give you troubles opening that file on non-Excel systems.What is better on my Win 7 laptop?
 7Zyp on AES256 encrypt OR
 Save Excel file go to Info>Protect Wordbook>Encrypt with password.