editing - QGIS split rectangular polygon in grid

I have this selected rectangular polygon in yellow on a layer with hundreds of polygons:

I need to split the selected polygon in 4 vertical columns (Y axis) and 8 horizontal rows (X axis), so that I get 32 final same-sized polygons. Something like this should be the output:

I have tested these plugins with no success so far:

• Polygon Divider


• Polygon Splitter


• Split Polygon


• Split Features on steroids

EDITED 19.12.2018:

Well in fact I have a layer with hundreds of polygons. It is my town's graveyard and it is divided in zones:

I need to split some of them in smaller tiles (real graves, pantheons, etc) so that I can locate each buried person in his parcel (tile).

In the above image I showed three zones. Polygon 1: has to be split in 1(columns)x 40(rows) so there would be finally 40 polygons (graves).

Polygon 2: has to be split in 2(columns)x 50(rows) so there would be finally 100 polygons (graves).

Polygon 3: has to be split in 2(columns)x 3(rows) so there would be finally 6 polygons (graves).

All the polygons that need to be split have square-rectangle shape; only 4 sides.

EDIT 20.12.2018:

Array of offset (parallel) lines tool is not working well in my case. Seems that rectangles are not perfect (horizontal sides do not have exact same length, same with vertical). See image below: