Guitar-> Source Audio Zio (analog pre-amp) -> H90 in/out 1 -> Quad Cortex–> Send Effect loop stereo -> H90 In/out 3/4 –> return to Quad Cortex—> output.
A simple solution would be to turn the Zio down a bit. It’s just set where I’ve had it for years with my presets. I just never knew it was clipping as I I never had my H9 pre quad cortex. It was just in the loop.