How to split a polygon in 9 equal parts but I want to use different orientation on QGis?

I want to split a polygon of a terrain that I generated through coordinates on QGis. But at the same time, I want to do perform such an activity by testing different orientations for the terrains being divided.

I know that there is a lot of calculus involved in irregular things like that, but I wasn’t expecting it to be so hard to manipulate different orientations for the polygon divisions. In this case, I got (with some trouble), the following orientation: "|||||". And it is not even good.

However, I want the terrain to follow this orientation: "////" or maybe "". I want the division to happen in diagonal sections instead of that. And on top of that, I barely can make it look decent because since it is an irregular polygon and I want 9 equal parts out of it, the Plugin "Divide Polygon" creates some crazy divisions in a block like aspect.

About the 2 different sections with 10 divisions on it, these are actually the method for me in order to create "stripes". In this case, sometimes the Divide Polygon plugin creates a perfect stripe. If not, I need then to divide the area into 20 parts and work around my way in order to assemble the division in equal stripes. As you can imagine, this is a tedious task and sometimes the "Divide Polygon" plugin gives you some crazy divisions (to my surprise, the plugin also is prone to make gross mistakes if you use it intensively. Like dividing an area set to 4 parts into 3 parts).

One last thing: Although I want 9 divisions on this terrain, I only got 8 showing in this image. This is because sometimes you can get a perfect vertical cut when dividing by two a large area. Then you can try to divide the new area in two as well and such. I am doing this but I do not like to deal with QGIS in this way.

I tried also several other answers made around that appear to correlate cases but I believe that this particular case that I am asking here wasn’t enough discussed on other threads. I need a simple and direct answer, and I tested several other methods and it wasn’t ever mentioned my specific problem on such cases.