Well, it's perhaps time to post a bit more here. I now have the Vipers back and have had them for a few days now. I also sent in my Nikon Monarch for an alignment check up as well. So I now am confident that there are no issues negatively affecting the view through either the Viper or the Monarch.
So, the decision on my part becomes which of the four Zen Ray binoculars do I wind up keeping and which go back. Right now my assessment of the binoculars is that there is no contest between the Monarch and the ZRS, both 8x42. I will keep the ZRS and the Monarch will go up for sale. The chief issues with the Monarch are the far superior depth of focus, the wider, flatter field of view and superior resolution of distant targets with the ZRS. The ZRS also has a locking diopter and much more solid eye cups. To the Monarch's credit, it does have a more neutral color bias than the ZRS and it is also lighter.
I will also keep the 10x42 ZRS and sell the Viper. This is largely due to the fact, I really do not use 10x binoculars much. The ZEN ED is a better binocular than either the ZRS or the Viper, but not much. So, the ZEN ED 10x43 will go back, the Viper is up for sale, and I will keep the ZRS. This is largely due to the simple economic fact that I will be able to get at least twice as much for the Viper as the ZRS will cost.
Additionally, when I got right down to a serious side by side with the ZRS and the Viper, there was no winner in what I could see in terms of detail. If I could see it with the Viper, I could see it with the ZRS. If I couldn't see it with the ZRS, I couldn't see it with the Viper either. I do have to say that the Viper appears brighter and certainly has a more neutral color bias than the ZRS.
I would suggest to Zen Ray that the future production runs of the ZRS might well be better served with a bit of a coating change to brighten up the image appearance just a bit. This is really the only criticism of the ZRS I can offer. The color is just a bit too reddish. But for $200 or so, it is still a heck of a bargain.
So, I will come out of this with the 8x43 ZEN ED, and both 8x and 10x42 ZRS. The ZRS will become the primary vehicle binoculars, replacing the Monarch and Viper. The 10x43 ZEN ED will go back.