I have a problem about zooming into the picture displayed in a picturebox
Without any source code, it is difficult to comment. StackOverflow is for problem solving; we can troubleshoot your starting code and get it working and during the course of which we can also fine tune design.
Anyway, I would like to give some pointers:
StretchBltis a powerful API that can be used to achieve. See MSDN documentation for details.
Gdiplus::Image. You can get enough info here:
Hope this would give you some starter.