I know that we can use matrix4x4.TRS() but I want to demonstrate about transformation order, so I use a quaternion for rotation and a translation matrix (4x4). But I do not know how to multiply it using “*” operator?

I also test to multiply a quaternion with a vector, then a translation matrix with a vector, but the result is different as testing with another tool.

As you can see they “kind of” generate a 3x3 matrix but without going through the Matrix4x4 class which would be wuite a bit overhead. However you can simply use this to create a Matrix4x4 out of the quaternion.

However it’s probably way easier to use

var rotation = Matrix4x4.TRS(Vector3.zero, yourQuaternion, Vector3.one);

Finally you can decide on your own in which order you multiply the matrices together.