Different surfaces, same isocurves

hi there, ive made this two polysurfaces and then i did a boolean union but what i really want is thar the share both the same isocurves (i tin thats the name) as i try to show in the photo belox

this problem appears when i want to render: the two differente polyssurfaces are supposed to be the same wall. I tried with a boolean union but rendering is clrear they are differente elements

Select the object and run _MergeAllCoplanarFaces.