Download older version of app

How do I download an earlier version of the software?

iPhone 4 ios 7.1.1

I would like to download

https://itunes.apple.com/us/app/izip-zip-unzip-unrar-tool/id413971331?mt=8

but the app requires ios 8.x

Since the app is on version 8.0, I assume there were iZip versions for 7.x.

How do I download an earlier version?

I read somewhere ios would promote me if I wanted to download an earlier version. I attempted to download iZip. I get the error message "This application requires IOS 8.0 or later. You must upgrade to IOS 8.0 ... The OK is the only thing to tap.