How to handle Key + Mouse Wheel simultaneously?

My camera code now looks like this:

    private void Update()
    {
        float zoomDelta = Input.GetAxis("Mouse ScrollWheel");
        if(zoomDelta != 0f)
        {
            AdjustZoom(zoomDelta);
        }
    }

I want to bind camera zoom to Ctrl + Wheel because I want to bind a wheel to brush size in my map editor. The problem is both Input.GetAxis(string) and Input.GetKeyDown(KeyCode) don’t work simultaneoulsy.

Turns out should use Input.GetKey(KeyCode) instead of Input.GetKeyDown(KeyCode).
Final code:

    private void Update()
    {
        if (Input.GetKey(KeyCode.LeftControl))
        {
            float zoomDelta = Input.GetAxis("Mouse ScrollWheel");
            if (zoomDelta != 0f)
            {
                AdjustZoom(zoomDelta);
            }
        }
    }