I'm not really one who is into cables a great deal, but many others are and believe they help so I will hope the effects are what you are hoping for. Yes, I agree the PM3 is excellent for my taste, loved it as a portable for sure. It is actually a major accomplishment that Oppo came to the market with three arguably excellent and well priced offerings right out of the gate. I felt the PM3 was very well made and worth the asking price so I have no regret having owned it and I am keeping my eye out for the next Oppo headphone which I am hopeful will come out sooner as opposed to later, but I have no idea if it will ever happen, just hopeful.
I think with any new signature time is needed. I liked the Z1R right away, but it started to really wow me over time. It has a difficult to describe (at least for me) presentation so it can sound understated and not cracking with energy, but the richness and even-handedness (yes I do feel the Z1R pulls off sounding balanced admirably) is captivating. I was away for two weeks, and upon return got very sick so I hadn't been able to listen to the Z1R for at least three weeks and last night when I finally found a free hour and was feeling well enough I took them for a spin. It was very nice. The Z1R seems to get out of the way while still surrounding you with a rich sound field. I think if you continue to just enjoy the music, try not to compare and analyze too much, just let the music flow, you will get acclimated to what the Z1R brings to the table. If in the end it doesn't float your boat, no big deal, no headphone is for everybody and there are so many excellent models out there anyway.
I'm loaning my Z1R to a friend for two weeks and he will be loaning me his MPH1000 so that should be an interesting exchange. Anyway, hope you continue to enjoy the Z1R.