No, but in practice if you put in a average zbrush model into maya because tehimporter needs to process a lot of data. Bu second to that mayas polys do use more memory than corrsponding structures in zbrush. AND there is a limit to how much you can use memory (its NOT maya limit its a COMPUTER limit)
But thats not the point point is if you intend to intergrate maya with zbrush BOTH applications would need to be built anew ground up. Because both have different modells for how to handele polygons. Because the LAST thing you want to do is have a intact ZBRUSH memory structure and a MAYA memory structure loaded at once ecause then suddenly you have 2 times the data in memory.
Anyway maya COULD work as zbrush does allready all it needs is a bit of rearanging is made to how maya pushes poly geomety about in thye DG. So that maya users could only push whats visible. And drop the rest temporarily. THJis would make painting with artisan viable again.
Anyway look out for mudbox, wich is essentialy zbrush without the ridiculous interface!