The expression pedal mapping being bypassed when the patch is made globally. I also deleted all expression pedal mappings on a few various effect algorithm presets with no apparent improvement in the zipper noise.

So is the issue of zipper noise when using an expression pedal to control overall volume one that can't be improved because there are simply not enough computational cycles left after the wonderful Eventide effects are crunched?

If you turn on expression control global input, it will ignore all expression mappings. If you set it on a preset by preset basis, it won't ignore the mappings. That's why I suggested you unmap the expression controls.

I just tried my H9 with an expression pedal controlling global input volume. It worked fine and I didn't experience any zipper noise or latency. Do you have this issue on all algorithms? Can you shoot a short video to demonstrate this noise?