Seems to be a modified ZBD-04B chassis. The headlight shape almost fooled me into thinking that it's a modified ZTQ-15 chassis, but after reviewing previous pictures, all signs pointed to modified ZBD-04B chassis (chassis lengthened to 7 road wheels, hull roof lowered) which make sense for commonality and maintainability.
It could even be a heavily modified ZTQ-15 chassis. I had just re-reviewed the possibility of modified ZTQ-15 chassis and I looked up VN-17 IFV which is proposed for export because it basically uses ZTQ-15 chassis that's driving backward. Compare its running gear with the new howitzer's and the similarity is uncanny.I think the chassis is a lengthened version of the existing PLZ05 chassis, which is not based on ZBD04. The chassis was first designed in the 1980s – long before ZBD04 was even on the drawing board – and is also used on PLZ45, PGZ95, and PGZ09.
Magazine based autoloader. Turret lowers the used magazine. It gets removed. New magazine is on the ground and gets hoisted in. To do all that, you need an overhang on the rear.This turret is massive. It goes beyond the chassis itself. Why the need to such a massive turret?
Well, the russian 2S35 also has autoloader, but its turret doesnt go beyond the hull:Magazine based autoloader. Turret lowers the used magazine. It gets removed. New magazine is on the ground and gets hoisted in. To do all that, you need an overhang on the rear.
Honestly, the overhang looks like its just some machinery or electronics (it only seems to cover the turret sides on the rear), as seen below (though that could be with the magazine removed).