There is 2 groups of vertices selected. Those that are up and those that are down. I try to move the upper vertices down and the lower vertices up, so that it can be symmetrical as if it has a mirror modifier in the Z direction. If you watch the video, you will understand easily what I mean. https://drive.google.com/file/d/1ka2SrB2bD2yJULcjnXJVY1rSWO7ZJSqG/view?usp=sharing
