limits are here:
http://blah.winsmarts.com/2008-4-SharePoint_limits.aspxregarding max per zone: it is the same as max per page. you could have all of them in the same zone. doesn't matter.
regarding the max # zones per page: i would say this is theoretically limitless. it's like asking the max number of lines or characters or borders you can have per page. zones are content holders. they are like an html table... you could theoretically have a limitless number of html tables on a page.
