The Zings are aluminium whereas their Nova siblings are brass. But then the Zings are solid, I believe, and the Novas are hollow. In a recent test I found the Novas are the heaviest of the Knitpro range (at least of the ones I stock).
I also decided to add an Addi lace circular to my death row (because I'm curious). All are 2.5mm diameter. One thing I'd not noticed before - the Zing tips are slightly longer than the others.
Note the careful measuring above - this is important because as you'll also remember, here we're demonstrating 'moments', in short the distance the weight and the fulcrum (the table) are apart will determine how easily the needle bends. All that matters is that it's the same for each test. 4" of needle protruding and the weight 3/4" from the tip.
The heavier Nova comes out on top, but not hugely. Both flexed quite a long way as the weight was added, but as mentioned earlier, if the needle sprung back straight when the weight was eased, then we kept going. The difference is the point that the needle wouldn't spring back.
As you can see, at the eleventh hour I condemned an Addi Premium too (aka Turbo) - the Lace bent so much more easily than the Knitpros (It surprised me - I destroyed the other end as well to be sure). I wanted to see whether there was a difference between their lace and premium needles. But both seem in the same ballpark, and can take around half the punishment of the Knitpros.
The Zings will bend (permanently) a little sooner than Novas, but both take quite a bit of force before bending. Around double that of a competitor. There are plenty of other differences that should also come into your decision - tip taper and sharpness, finish, tip length (noted above), whether the size is marked on the needle and colour of course - users are loving the colours of the Zing range and that's important.
Buy Knitpro Zing needles here, buy Knitpro Nova needles here, and Addi lace needles here and Addi Premium here
Thanks to Mister Percival. I know we gave you a hard time but your efforts weren't wasted. I also notice that I mix imperial and metric units fairly wildly. A legacy for us children of the seventies!