The Zu Denon is very much a "salt to taste" kind of cartridge when it comes to loading. When I used one it could indeed sound quite different when using 100/200/300/500/1000 ohms. And Zu will tell you there is no wrong answer here, just use what sounds best to youAgain: loading has no effect on the sound of a **low output** cartridge- it has everything to do with the stability of the phono preamp.
@intactaudio While I agree generally with Peter in this regard, I am suspect of the idea that loading causes the cartridge to track better in all cases. I have seen this where the cartridge was otherwise incompatible with a tone arm; a good example is a Grado in a Graham 2.0. The loading prevents the 'Grado dance' that can otherwise occur especially in lead-in grooves. However that is all about tone arm compatibility, and as I mentioned earlier, when you load the cartridge it stiffens the cantilever. So you will get different results in different tone arms! Peter wasn't being entirely scientific in this regard as his data was limited to one tone arm/cartridge combination.