How to efficiently encode JPEG to support zooming into a specific section?

I'm using CSS animations to zoom into a specific (fixed/constant) part of a JPEG image. (Similar to the "Ken Burns effect".)

Is it possible to encode the zoomed section at higher quality, whilst leaving the rest at a lower quality? If the format supports this, what tool can be used to achieve this?

Solution

The compression settings are the same for the entire image frame. There is no way to change them for specific areas.