In most word processors it is possible to assign keyboard shortcuts to the various functions of the Zotero word processor plugin toolbar (i.e. add citation, edit citation etc.). How to do this depends on your word processor.
See this blog post for longer, illustrated instructions.
The keyboard shortcuts for the plugin actions are shown in the AppleScript menu. They use the Control and Option keys.
The Shortcuts of the AppleScript Menu are handled in the filenames of the scripts. To change them go there via:
Script-Menu (where the Zotero Menu is located in the Menu Bar at the top of the screen) → About this Menu → Open Folder
Or by path there, which is: '/Users/yourusername/Library/Application Support/Microsoft/Office/Word Script Menu Items'
You can there see the Keyboard Shortcut after the Backslash.
c stands for Control, m for command, s for shift and o for Option
At least one of c (Control) and m (Command) must be included and s (Shift) and o (Option) are optional. So a sample name for assigning the 'Add Citation' to CMD+A is: 'Add Citation\ma.scpt'
This will also update the Menu entry to the new shortcuts.
See here for more details.
Tools menu –> Customize keyboard…
In the Categories list, select Macros.
The Zotero commands will appear in the list on the right. You can view and modify the keyboard shortcuts using the controls on the bottom of the dialog box. See here for more details.