How to change .zip to .mcpack on iOS
Solution 1:
Yes you can change .zip files to .mcpack or .mcworld, because zip files and mcpack/mcworld files are both zipped files. All you have to do is change the file ending on your PC.
Here is an answer that I found by someone else about the same question here:
"The .mcpack is just a new extension name for a ZIP file. Make sure to have "View > File Name Extensions" turned on in Windows Explorer when changing the file extensions. Also to make working .mcpack files, you'll need to create the manifest.json correctly. There are a few other points."
So just change the file ending while the file is on your PC, then when your iOS device gets it, open it like you would normally. You can also get file managers from the Apple App Store to edit it.