How Google Super Res Zoom in Pixel 3 improve Digital zoom

Traditionally, mobile device cameras uses software algorithms to implement digital zoom. Compare with the optical zoom capabilities of DSLR cameras, the quality of digitally zoomed images has not been competitive.

The Super Res Zoom technology in new released Pixel 3 is different and better than any previous digital zoom technique based on upscaling a crop of a single image, because it merge many frames directly onto a higher resolution picture.

This post (from Google AI Blog) explain Super Res Zoom algorithms in details:
See Better and Further with Super Res Zoom on the Pixel 3