Omero Capanna

Arrow 4K Blu-ray is is a bit stronger than the very good Blue Underground The differences in the body of the film are negligible, but Arrow does have all three main credit sequences (Zombi 2, Zombie Flesh Eaters, and Zombie) that play in 4K via seamless branching. They also un-stabilized the handheld shot in the Zombie closing credits that Blue Underground had stabilized when they added new digital titles. It's back to looking properly handheld.

Arrow 4K Blu-ray > Blue Underground 4K Blu-ray, "has the original Italy mono - think someone said earlier that the Blue Underground was a downmix on that track and the Arrow is corrected"

4K restoration from Original Camera Negative

Cohen Blu-ray is the best with the least amount of DNR or sharpening among Germany StudioCanal, UK MoC and France Gaumont. Even though Cohen doesn't have the best encoding, it's definitely the most superior release. See caps-a-holics caps

Italy Medusa Blu-ray is the 4K resto but boosted contrast and colours. Still probably better than Criterion

France Pathé Blu-ray is the 4K resto and best encoding

The Paramount 4K "restoration" is a desecration. It has completely revisionist color timing, harsh HDR, treatment of stock footage, bad encoding, selective DNR and grain management so bad that the entire screen frequently freezes up with only characters moving around in grain soup. It is so bad that the film's restorer Robert Harris publicly washed his hands of it saying essentially the 2007 restoration (with Willis and Coppola supervising) is how the film was intended and made. This is Paramount's modern version done their way. The new 1080p SDR Blu-rays in print are the crap 4K desecration master with the same problems still there just harder to spot and with crap encodes. Part III fares best of the three and these issues are at their most minimal-but they're still there. The new Coda version is given prominence with lesser encodes for the other two versions. The original mix was remixed into 5.1 decades ago and we have yet another version of this instead of the original Dolby Stereo SR as heard on the LaserDisc release.
The 2008 Blu-ray of the 2007 restoration, while an imperfect outdated disc, is LIGHT YEARS better than this 4K desecration. The only truly major issue is that it is very slightly redder than the 2007 finished master as seen on DCPs.
DFIC review of the hideous crap 4K Blu-rays: https://youtu.be/0uw6-Kcy_UA?si=ob1nDg0wTCvemjH0

Despite being restored alongside the Coppola Restorations of The Godfather: Parts I and II, the Part III restoration is not officially labelled a Coppola Restoration.