How to get rotation between rotations?

Question

C++ / C#

There are two Quaternions. It is necessary to get such a Quaternion, when multiplied by the first Quaternion, you can get the second Quaternion.

Answer 1

Quaternion is a completely Russian word.
In total, we have quaternions A and B, we want to find such a C that
AC=B
means that by multiplying both parts on the right by the quaternion inverse to A, we can get
C=invert(A)B.
Quaternion inversion - take the conjugate quaternion and divide by the square of the norm. It's all there on Wikipedia.