Hello EEcontrols,
Thank you for using Apple Support Communities. Based on your post, you can't adjust photos by zooming to set as wallpapers. We'll do our best to assist with this.
The ability to zoom by pinching the photo in or out, depends on the photo itself. Not all photos have the ability to do this. See section, 'Move the image and choose a display option' here: Change the wallpaper on your iPhone
You may want to select a different photo to use as a wallpaper, if you can't zoom it in or out.
Hope that helps out, take care!