Adjusting aspect ratio/zoom level of original clip in split screen. Please help!

I'm trying to play two videos side-by-side, simultaneously, both of them playing in their original aspect ratio (fully zoomed out). I've had no problem getting the split screen function to work, and I am able to then adjust the zoom level on the second video and have it appear in its original, wide-screen format. But try as I might, I cannot figure out how to get the original clip back to it's fully zoomed-out, wide-screen appearance. (It's displaying in the cropped, square-ish split screen aspect ratio.) I've tried on my phone (iPhone 6 Plus) and my iPad (Air 2). Any ideas? Thank you, in advance, for any help.