Unity (until Ubuntu 17.04)
Unity Tweak Tool
Other than the Compizconfig Settings Manager, a new configuration tool is now available called Unity Tweak Tool.
Open Dash (by tapping on Super) and type "Unity Tweak Tool".
If it is not available, you can install it from the software center (Unity Tweak Tool ), or you can install it from the terminal with:
sudo apt-get install unity-tweak-tool
Open the application, and from the icons choose
General under the
Window Manager section.
Once you click General, enable the "Desktop magnification" option at the top. And you can change the default keyboard shortcuts of the Zoom In, and Zoom Out functionalities.
As seen in the next screen-shot, I have the Zoom In set to Ctrl+Super+Z and the Zoom Out set to Ctrl+Shift+Super+Z
Personally, I prefer including the Super key to all system wide shortcuts so it won't interfere with a certain application's shortcut.