Abhishek, Alejandro, welcome to IDLE development! If you can, please sign a contributor agreement.

We have two patches to create this enhancement, both are good. I suggest that we figure out how to merge the solutions.

The zoom-out binding should also include Ctrl-Equal, so that holding shift is no longer necessary. There's also a corner case where the zooming in on the editor may cause the cursor to go outside of viewing window.

Using idleConf to query the font information is not strictly necessary since the font configuration in the text widget contains the font size already.

In the future, please be careful with licensing. The top part of the ZoomFont.py extension places it under the NCSA license. Fortunately UIUC has allowed me to relicense parts IdleX for the Python Software Foundation.