How do I zoom in one window in Unity
There's another plug-in if you open the compiz configuration manager (ccsm) called "Enhanced zoom Desktop". There you can define the key binding for the zoom, and keys to zoom only an area or a window.
In case you don't have that option, or even the ccsm, you will have to install the packages that includes the extra plug ins. I do it trough synaptic in every new Ubuntu installation. Just search "compiz" and install all the available packages (except the KDE related ones).
Wish it helps, good luck!