With a 6.5 pound rifle with a 16 inch barrel, it seems like you would want to put the lightest scope possible with a low end magnification range. Seems like the perfect dense woods hunting rifle. As mentioned above, it really has to do with the intended purpose of the rifle. The swfa ultralight 2.5-10x32 seems perfect on paper but I have no experience with it. In the same basic price range you also have the luepold vx freedom 3-9x40. If you could find a used vortex razor hd lh 1.5-8x32, that seems like another great choice.
Of the 2 you listed, I would go with the viper because the power range seems more appropriate for the rifle. The zeiss has better glass but I would prefer a 2.5x magnification over a 4.5x magnification on the low end. You will get a much better field of view with the vortex. If you are just going to be shooting at the range and maybe some open field type hunting, the zeiss would be the better choice.