Fabian D.
DS tracks and allegedly a complete new and simpler tooling.

From Dragonmodelsusa.com:
"Dragon has offered kits of the Ausf.D before, but this latest model is a brand new item that utilizes completely new toolings. Indeed, the only reused components on this 1/35 scale plastic kit are the on-vehicle tools, and the DS tracks that have been used on Dragon's previous Panzer IVs. This completely refurbished tank thus gives modelers a Panzer IV D built to the very highest Smart Kit levels. Furthermore, the highly experienced design team has sought to minimize the number of parts wherever possible so that model-makers are spared the ardor of repetitive assembly."

Urban Gardini
Thanks mate! I'll stick with my #6265 then...

Fabian D.
There is hardly anything better than those old smart kits...

Urban Gardini
A lot of parts but they're more or less unbeatable!

huenlil
Some test shot from Platz
platz-hobby.com/products/5944.html

Aus78Formula
The downloadable instructions are incorrect for the Pz.IV on this page, see paint markings.