Yes and no.
No, all of the parts of the Ziva plugin run at the same speed in any version of Maya.
Yes, Maya 2018 has a horrible performance bug causing meshes that take a few milliseconds to process in Maya 2016 to take multiple seconds in Maya 2018. This is independent of Ziva's plugin and can easily be triggered entirely with built-in deformers. If you're using more than 1 simulation substep per frame (zSolver.substeps > 1), then this Maya problem may be triggered and can significantly slow down everything. The workaround is to set Maya to playback at the same rate as the solver substeps. For example, if zSolver.substeps = 4, then set "Playback by" in the Time Slider preferences to be 0.25 = 1/4 to match.