As of iOS 13 your recipients can choose to save our Zip file to Apple's Files app on their iOS device.
- You must send 2 or more files for the zip to be created, a single file will not download correctly
- Your original files must be in an iOS friendly format and encoding
- Click the normal download all button to the top right of the files
- After download safari will display the zip file with options
- Select the 'More...' option below the file
- Select 'Save to Files' item
- From the Save menu displayed select 'On my iPhone'
- You can then open your Files app, you can select the zip file and it will unzip to a folder
- From there files can be either saved to your camera roll or sent directly to an app (Instagram, Facebook etc)