I have a fairly extensive wiki on ZWiki on Zope (in turn on Plone). Most pages are in reStructured text format, but there are several in straight HTML as well.
What is the best approach to migrate those pages over to a MediaWiki wiki with pages converted to MediaWiki and HTML formats? Of course I'd like to automagically convert all links (internal and external).
I've no experience of ZWiki and don't know how large your wiki is. But general advice - you can use find / replace in Notepad or Notepad++ - or you can write a macro in Excel.
This is per page copying which is only really suitable if your wiki is not larger than, say, 1000 pages.
I suspect you'll still have manually to check each page though, and update your scripts accordingly.
Good luck with it - I suspect you'll be pleased with the final result because MediaWiki is pretty awesome.
Update: one disadvantage of moving to a new wiki is that you will lose the page history (i.e. who wrote what, when).