Help with quaternion multiplication

[pixartist]

I have finally managed to convert absolute quaternions to navball quaternions like this:

public Quaternion ReferenceToWorld(Quaternion localRotation, FrameOfReference reference)
        {
            switch (reference)
            {
                case FrameOfReference.Navball:
                    return (OrbitalOrientation * localRotation) * Quaternion.Euler(90, 0, 0);
                default:
                    return Quaternion.identity;
            }
        }
        public Quaternion WorldToReference(Quaternion worldRotation, FrameOfReference reference)
        {
            switch (reference)
            {
                case FrameOfReference.Navball:
                    return (Quaternion.Inverse(OrbitalOrientation) * worldRotation) * Quaternion.Inverse(Quaternion.Euler(90, 0, 0));
                default:
                    return Quaternion.identity;
            }
        }

Now I would like to do the same conversion with vector3s. The problem I have is, I can't apply the Quaternion.Euler(90, 0, 0) last, because you can not multiplay Vector3 * Quaternion. How would I have to rearrange this in order to keep the result but have the local/world rotation last in the multiplication order ?

[S1gmoid]

I'm not sure I understand what you are trying to do. A Vector3 that contain Euler rotations, or a Vector3 that contains a unit vector in 3-space?

[pixartist]

I'm not sure I understand what you are trying to do. A Vector3 that contain Euler rotations, or a Vector3 that contains a unit vector in 3-space?

A direction vector, e.g. unit vector in space coords.

[ratchet freak]

you can apply the rotation to the vector, (you know it's why the quaternion is even there: represent a rotation )