I don't think those numbers are limited.
MC can import hundreds of thousands files and work fine with such a media library. Naturally, with a huge library MC's responsiveness and overall performance is dependent on many factors, like the file formats, drive access speed, the amount and complexity of the library fields (you can create various kinds of calculated fields) and so on.
My modest library of 60,000 files is nowhere near the practical limit even on my oldest PC, a 1.4 GHz AMD Athlon.
Regarding the zones, as a test, I just created 65 zones without problems. However, the zones in MC may not be exactly what you think. They are just memorized settings for individual playback queues. When files are played in a certain zone MC can display a zone specific Playing Now list and it uses whatever output settings you have set for that zone. For outputting audio to separate devices you need to have the devices installed on your OS. You can switch between the zones and launch multiple playback queues. The number of possible simultaneous playback queues is limited by the PC's performance. Also, the maximum number of separate audio devices may have a practical limit.