How can I write in Tikz:

[![enter image description here](https://i.stack.imgur.com/IlK2H.png)](https://i.stack.imgur.com/IlK2H.png)

One difficulty I have is to write over and under the arrow. I've looked up several solutions but I'd prefer a basic solution that doesn't go into nodes and stuff. Is it possible to do it with this kind of syntax?:

```
 \arrow[rr, leftrightarrow, "*"]

```

I have no idea how to draw the oblique lines on the left and right side...

A further challenge that I have is to draw curved lines with the above simple syntax as in the following image:

[![enter image description here](https://i.stack.imgur.com/CyYXp.png)](https://i.stack.imgur.com/CyYXp.png)

**Edit:**

Curved case is solved thanks to @marmot with the following code:

```
\begin{tikzcd}
x \arrow[rr,leftrightarrow,"*"] \arrow[rr,bend right]  & & y 
\end{tikzcd}

```