The text on the 2nd image says that the Leica 1600mm f/5.6 can become a 3200mm f8 with 2x Teleconverter, but that should really be a 3200mm f11. A huge chunk of glass either way (60kg). Also see ....
https://www.apotelyt.com/photo-lens/...yt-r-1600mm-56
I'm working on my own version starting with a Nikkor 600mm f/4 and then adding stuff....
Best
JA