For my eyes, the Z6 has better glass than the V6.

I had tracking issues with my Z6, a first generation 3-18x50, which I sent back to Swarovski to be serviced and trade it away thereafter.

My experience with V6 is limited to a 2-12x50 and a 2,5-15x56 and so far they are 100 percent. Very good optics but like I say, Z6 were even better, at least for my eyes.