Update: you can’t rebind to Ctrl+Shift+Z because Ctrl+Shift+Z is already in effect. It’s just that Dynalist can’t show two shortcuts for the same action.
I meant you don’t need any binding at all to use Ctrl+Shift+Z, that’s enabled by default (this is why you can bind to it – it’s already bound to it).
You can bind to Shift+Z and then to Ctrl+Shift+Z, or you could remove the binding altogether.