The original zentrix.tv website was taken down in 2010 when the Imagi animation company that produced Zentrix closed down.
The Internet Archive Wayback Machine was able to help me out and had preserved the entire lot.
Where images are not available in 1280*1024 resolution, this looks to be due to the files not actually having been added to zentrix.tv originally.
Either, there was no link in the HTML or the link led to the wrong file, preventing the Wayback Machine from acquiring them.
In those cases, the 1024*768 image was downloaded instead.
I checked later snapshots of the website and the wallpapers that were missing in 1280*1024 resolutions were not added later.
Essentially, the website was never updated after it was uploaded in 2002.
The filenames shown here have been fixed and simplified.
Where 1280*1024 (5:4) outputs exist, the images appear to have been created at this resolution originally.
The 1024*768 versions were created by cropping the 1280*1024 originals to 4:3 and downsizing them.
In any event, I'm really pleased that these are still around. They're probably the best-quality renders that we'll ever see of some unique and inspired machines and characters.
Cool Ships - AS-5 Proteus
Cool Ships - CA-FMF66 Blizzard
Cool Ships - Space Above and Beyond
Games - Fury3
TV Shows - Dan Dare
TV Shows - Firestorm
TV Shows - Max Steel
TV Shows - Terrahawks
TV Shows - Xcalibur
TV Shows - Zentrix
French - Disc 1
French - Disc 2
French - Disc 3
French - Disc 4
Volume 1 - Disc 1
Volume 1 - Disc 2
Volume 1 - Disc 3
Volume 2 - Disc 1
Volume 2 - Disc 2
Volume 2 - Disc 3
Zeus Action Figure