This is just my personal setup of the Microsoft Natural Ergonomic Keyboard 4000 on Ubuntu which does various remappings that I like.
Create new file /etc/udev/hwdb.d/61-keyboard-local.hwdb
and insert following there:
# Microsoft Natural Ergonomic Keyboard 4000 - remap zoom in/out to up/down
evdev:input:b0003v045Ep00DB*
KEYBOARD_KEY_c022d=up
KEYBOARD_KEY_c022e=down
Copy contents of the configuration file from below and run these commands:
sudo udevadm hwdb --update
sudo udevadm control --reload
After that unplug and plug the keyboard.