USDZ created in Keyshot

[Renderhouse]

I`m using Keyshot 10.1 and I have massive problems creating USDZ. When I export USDZ`s it often crashes. It`s more stable when I use the export AR function. The it creates .usdz and a .glb file.
Since I`m always working with volumetric models I can't re-tesselate. I`m using very low quality in the export function.
What you see in the photo is 5,5MB big. It was a screenshot on my Iphone 8 (only Iphones support USDZ). The one display on the right is not correct.
I would like to create a USDZ of a industrial machine but the data size is too big (>1Gb). I read that 75Mb is max. for an Iphone.
Any ideas how to make the data smaller with too extreme effort?
I scaled the model to 0.1 but that didn't` make difference.
Deleting inner parts is very time consuming and helps a little.