Received my first Z-mount teleconverter, a 1.4x. It is quite a bit larger than the F-mount TC-14E III and noticeably heavier, but that is expected due to the wider lens mount. The front element of the Z converter sticks out quite a bit. And similar to its F-mount counterpart, it has an extra notch on the bayonet. I tried mounting the 1.4x TC behind the FTZ adapter, and as expected, the baffle on the FTZ blocks the long front element of the TC. The rear mount of the FTZ is also missing that notch, which is required to mount the 1.4x TC. F mount TC-14E III on the left, Z mount on the right. Both converters have an extra notch. Notice that the mount on the 1.4x TC has that notch in the 9 o'clock position. The Z6's mount has no such notch. On the rear mount of a long Z tele, such as the 70-200/2.8, there is a matching notch in the 4, 5 o'clock position, left. On the rear mount of the 1.4x TC and other shorter lenses, there is no such notch. Therefore, Nikon is preventing people from mount one TC behind another TC.