Triple tap with three fingers to zoom in and zoom out. While you're zoomed, drag with three fingers to pan the view.
But I also kinda feel like just saying that says a lot about Apple's UX these days, especially in the accessibility department. Because those swipe gestures can be confusing and require too much manual dexterity for many people who need a feature like screen magnification.
Re the other reply here, what's missing is discoverability -- at minimum a little circled letter "i" in the corner that would pop up a big sketch of the required gesture.
Discoverability is important, but elderly people are unlikely to be able to reliably (or at all) triple-tap with three fingers, regardless of discoverability. Many already have problems with double-pressing buttons (like for Apple Pay).
Triple tap with three fingers to zoom in and zoom out. While you're zoomed, drag with three fingers to pan the view.
But I also kinda feel like just saying that says a lot about Apple's UX these days, especially in the accessibility department. Because those swipe gestures can be confusing and require too much manual dexterity for many people who need a feature like screen magnification.