leif as you highlighted, the the zCache writes the simulation state to RAM - the intention behind this tool was to use it as a preview and rig debugging tool so that you could scrub the timeline and visualize the collisions, attachments, tet meshes etc. to inspect them for situations where things go awry.
The downside to this approach is that it will consume your system RAM in situations where you have a a long animation and/or a heavy asset (like Zeke).
If the goal is to write the result of the simulation out to disk for playback - don't bother with the zCache - and instead just write your muscle geometry out as an Alembic - this won't consume your system RAM.
I hope this helps!
-jj