Seriously, if the ZKK barrel is in such good condition that it justifies putting into another action then sell it to a ZKK owner and use the money to buy a new barrel specifically for the Mauser 98. (Aussie barrel makers Swann, Tobler, TSE etc will all do a barrel for a Mauser.)
I have to agree with Hunter here! I wasn't sure on the thread sizes at all, but to break up a ZKK602 is not really the done thing to do. If it has peeps sights on it then you will have a tidy sum sitting in your back pocket if you have to sell it. There is nothing wrong at all with the ZKK's, quite the contrary to that, they are a fine rifle indeed! If you do sell, that will easy pay for a new barrel & sights if you want it on a Mauser.