At your request, here's the code that I used for Burnikel-Ziegler division. As I said, performance was disappointing - although I wouldn't rule out bugs as the source of the problem.
I didn't get around to writing a formal set of test cases, but I also attach the test script that I used.
Patches to integrate Burnikel-Ziegler division
Burnikel-Ziegler division
Informal test cases for bignum division
thanks