Yes, there is. You can use the Onkey method to specify all sorts of shortcut keys for your macros. The only downside is that you need to set them when your workbook opens, and you should probably reset them when your workbook closes e.g.
Place this code in the workbook code module (see the workbook modules section from
here to see how to do that).
Private Sub Workbook_Open()
Application.OnKey "%z", "MyMacro"
End Sub
Private Sub Workbook_BeforeClose(Cancel As Boolean)
Application.OnKey "%z", ""
End Sub
The first procedure sets up alt-z to run the macro named MyMacro. The second procedure resets it when the workbook closes.
If you have a macro called MyMacro, it will be run when you press Alt-z. Look in the VBA help file for Onkey and you'll find a full description of what it can do.