How rotate diagonally a cube

Hi, i’m a beginner.
How can i rotate my cube diagonally?

Rotate the X axis and the Z axis at the same speed. That should work!

Rotation always happens around an axis. usually you rotate around x, y or z axis. In your case, you use a diagonal axis like

new Vector3(1,1,1);

which points into the upper forward right corner. Use it like this:

transform.Rotate(Vector3.one * Time.deltaTime);

where Vector3.one is shorthand for a Vector3(1,1,1);

Rotate has a last default parameter which is set to Space.Self, which means it does not matter how the cube is rotated in the first place, the rotation stays the same relative to that cube.