Kind of an oversimplification here: Moiré is a form of interference pattern, in this case the “grid” of OP’s image has a different pitch from the grid on your phone or computer display. By continuously changing the zoom (in contrast to discontinuously), the interference pattern shifts to create “peaks and valleys.”
Here’s some more info: https://en.wikipedia.org/wiki/Moiré_pattern
Kind of an oversimplification here: Moiré is a form of interference pattern, in this case the “grid” of OP’s image has a different pitch from the grid on your phone or computer display. By continuously changing the zoom (in contrast to discontinuously), the interference pattern shifts to create “peaks and valleys.” Here’s some more info: https://en.wikipedia.org/wiki/Moiré_pattern
https://www.youtube.com/watch?v=4nn1MqCMa1M