Butterfly Viewer can view multiple images side by side with synchronized panning and zooming. Simply drag and drop image files into it and it'll auto-arrange them as a grid, column, or row.
I'm the creator, and I recently released it to the public on GitHub.
You can install it on Windows, run it as a package for MacOS (beta), or run it directly on its Python source code.
GIF of drag-and-drop with synchronized zoom and pan. Image of six photos individually panned and zoomed.
