Okay, so while working on your scene we found a MAJOR performance bug introduced in Maya 2018. The problem isn't at our end, it's with the Autodesk API and we're filing a bug report.
The good news is we have a work around which could give you as much as a 100x speed gain in your scene.
Basically you need to force Maya to jump to the solver subframes when you playback your animation. So in your preferences, change this:
If you're running 4 substeps you need to change this value to 1/4 (0.25) If you're running 8 substeps, it would be 1/8 (or 0.125) and so on.
The problem is specific to bones. You won't see the issue until you have ziva bones in your scene.
Now that I have that out the way I can continue going through your scene! 🙂