“Zooming with your feet” means getting closer to your subject physically instead of relying on a longer lens, but you should be aware that the results you won’t be the same. Here’s a 9-minute video from This Place that looks at how different focal lengths affect perspective when compared to “zooming with your feet.” Perspective distortion is often misunderstood — it’s an area of photography that many photographers may not need to explore or understand properly.
Source: This is Why ‘Zooming with Your Feet’ Isn’t the Same Thing