I've already found the max number of web parts per page:
Customizable - in web.config file,
<configuration><SharePoint><WebPartLimits MaxZoneParts="XX" />
50 (default) - http://technet.microsoft.com/en-us/library/cc262787.aspx
100 (recommended max) - http://technet.microsoft.com/en-us/library/cc287743.aspx
However, I've been unable to find:
the maximum number of web parts per web part zone
the maximum number of web part zones per page