I converted my NZATPL to a HKCAD ATPL 12 years ago and I only had to do some exams, from memory it was only ATPL law, human factors and performance. I know the Australians I were with at the time were required to sit extra ATPL exams, can’t remember why?
I most definitely were not required to to any PPL or CPL exams. I was only required to do exams appropriate to license you’re converting.