Hi Tristan,
Sorry for the late reply, I've replied your support mail and bring more info. Let's discuss more details in it.
Regarding the texts in the Ziva VFX documentation that "iterative solver doesn't support inertial damping", this is our mistake that didn't update the document on time.
In v2.1, the iterative solver is full-fledged and supports all features that direct solver does.
Regards,
Chengdong