zimg is the scaling library built into vapoursynth. So the vs.resize.xxxx functions are Z.Img routines. (And I used a lot of Vapoursynth's Resize docs in figuring out stuff for ffmpeg zscale filter :P).
So after using zimg / vs.resize to convert to linear RGB in floating point, you can tonemap with basic math in Python if you know the algorithm. The thread about it you're already active in:
https://forum.doom9.org/showthread.php?t=174415