Hello Jim,
To control the enlarge image add this below CSS in the custom.css
.mx-imagezoom { background-color: #000;}
img.mx-imagezoom-image { width: 100%; height: auto;}
for pinch in & out, we also trying to find a solution.
Does this widget still work? https://appstore.home.mendix.com/link/app/65122/Mendix/Image-viewer
It’s not the default image viewer, but I believe it should suit your needs.