Xezon recommends using XCC Mixer to change your hotkeys. You can download it from the Downloads: Miscellaneous page (scroll to the bottom).
After opening XCC Mixer, make sure you go to File -> Open, then browse to your C&C Generals Zero Hour installation directory and double click the EnglishZH.big file. From this point onwards you can follow the rest of Xezon's tutorial:
Xezon does a great job explaining it all and this video really helped me with changing my own hotkeys.
I have completely re-done and re-mapped all my hotkeys. If you want to give my hotkeys a go, you can also find them on the Downloads: Miscellaneous page.
These are my personal hotkeys but I've put them online for people to try. My set-up is designed for right-handed users. You should rest the fingers of your left hand on the keys 'A', 'S', 'D', 'F' (just like with touch-typing), and rest your thumb on the space bar. All hotkeys will be in very close proximity to the resting position in order to increase speed. When playing, always try to return your fingers to their respective resting positions.