Trouble with soild union


Ultimately I’m trying to create circular window holes in my structure. I’ve been trying different methods to achieve this, like trying to trim the surface with the circular curves (I have the outlines for the window), but it doesn’t work, because I’m pretty sure you’re only supposed to trim one surface at a time when I have a lot of faces on my structure.

Then I tried extruding the structure walls to give it volume, as well as extruding the windows to use boolean difference instead to carve out the windows in solid form. But it failed I’m assuming because there are too many components overlapping, and I couldn’t solid union them together because not all of them intersect.

Here I tried doing it in rhino space manually, and it works just fine (not if I select all and type in the command) only when I do small segments of it, but nevertheless with the same commands.
Fail Soild (538.1 KB)

Any suggestions or commentary would be greatly appreciated,