Well, that's an interesting combination - Sigma and Zeiss.
Both top quality lens manufacturers that deal in different operational concepts - one looking to make a number of value-packed zoom lenses and one seeking the prime market. The good thing for users of Nikon and Canon camera bodies is that many of their products can be found with mounts for these brands.
But consider - you might find Sigma or Zeiss lenses on a lot of camera bodies. We can think of Zeiss lenses on Fujifilm X-series, Sigma on Olympus and Panasonic, Zeiss on Leica M bodies, and a number of Zeiss's devices associated with Sony.
Come to think of it there are adapters that allow these products onto a lot of micro 4/3 or other mirror-less bodies. A bit of a juggle sometimes but surprisingly do-able nonetheless if one is prepared to focus and set apertures manually. A lot of studio closeups for this column are taken with an adapted lens that started on a DSLR and now fronts a mirror-less camera. It's not speed-demon work but yields a fine focus.
Anyway, there is to be a $200 cashback for these items today - Tues the 15th of December. $ 200 is large coarse money for many citizens and not to be disparaged by any means.
By the way, when you stop by the Sigma cabinet at the front of the shop take some time to inspect the aluminium lens barrel from a Sigma lens that is displayed there for effect. It is comforting to see the level of precision that is buried under the black paint.