I don't have the Windows kernel source code but I strongly suspect that they could reduce the memory used by zombie processes if they thought it was important.

I don't have the Windows kernel source code but I strongly suspect that they could reduce the memory used by zombie processes if they thought it was important. The only operations that I am aware of that can be performed on a zombie process are CloseHandle, WaitForSingleObject, and GetProcessExitCode. The page tables and private memory shouldn't be needed for that. I'm curious as to what you think the 64 KB of memory is actually needed for?