Ive heard muzzle the 2 dogs and leave them together. If/when they fight they cant injure each other. One will come out on top and settle pecking order then should be ok.
fox terriers,teckel,jagdterrier.at the moment we have about 60-70 black dog,
not many but hunters here have become interested in that type.
Apart from Teckel and Jagd are there any other terriers that are not from UK?
Let him get used to sight and smell of the ferrets, exercise and tire him out before hand to make him easier to handle. Push him away each time he shows to much interest. When he stops taking to much interest inthem in the hutch,start handling them in front of him and do the same. When he realizes that their not prey he will settle.