Dave, I believe that it's a combination of two factors. First, the Z 70-200mm f/2.8 lens is better than the earlier Nikon F-mount versions. It's optically superior, proven both in MTF charts and in real world testing. Second, I believe, but have no hard proof, that the Z 1.4X and 2.0X TCs are better than the earlier Nikon F-mount TCs. Like you, I've used TCs in the past with mixed results. When I was into photographing birds in flight, I'd use a Nikon 500mm or 600mm lens, sometimes with a TC. The TC results were inferior to those shot without a TC. I never got usable results with a 2.0X TC. The 1.4X and 1.7X TCs were usable but there was some image degradation compared to the photos using a bare prime lens. Now with the Z 70-200mm f/2.8 lens, I feel comfortable using either the 1.4X or 2.0X TC, even hand-held. Color me impressed.