This creates visual effects of something crashing into focus, with the idea of you starting on a point, then as you close the shutter, moving the zoom or your camera. Either way will work, but it takes some practice! The slower the shutter speed, the more dramatic the effect.
Example from Katy Eacott
I tried 1/5 and 1/8 of a second, zooming in and out. I adapted the aperture and found F22 – 29 worked best when outside.
Photographer: Katy Eacott