"What would a Hizack be like in the GQuuuuuuX world?"
This is a work created from that idea. It's a diorama.
The Hizack in this work is set to be a modified Zaku-based machine made by the Titans for use in top-secret operations.
While transporting a ridiculously large outdoor unit to Side 6, it turns around and kills a suspicious military and police Zaku...that might have been the scene.
Basically, the lower half of an HG Hizack is forcibly fitted onto the upper body of a GQ Zaku, and the upper arms and below are also forcibly fitted together using 3mm plastic rods from the Hizack.

A fratricidal conflict. | フォイヤーヴェルク's Gunpla works