The zoom in and zoom out transitions from Day 21, built on an adjustment layer with motion blur.
How it's built
- Adjustment layer 15 to 20 frames on both sides of the cut, Transform node in Fusion.
- Zoom in: size 2.5 on the last frame of clip one, 0.25 one frame later. Zoom out is the reverse.
- Edges set to Mirror, motion blur with quality and shutter angle maxed, keyframes eased with F.
Full walkthrough in Day 21 on @julianhoenger.