So their was a really cool mod I liked, which was a complete over haul and conversion http://www.bay12forums.com/smf/index.php?topic=120494.msg3876546#msg3876546 <link to mod right here
and two awesome mods put together make's a even more awesome mod, so I want to know how I can merge these two mod's so I can play both at the same time, but when I tried this I only got a crappy glitchy mess which broke down in 1 second, could someone please help me out with this?
You can try dropping the 40k's raws and hack/scripts folders into MDF, merging the mods together. You will have an insane and crash prone game because that's like trying to merge brutal doom with demonsteele.
Merging a total conversion with pretty much anything is hard. And that one in particular? You'll have a bad, bad time.
In short: you need to pick what will supersede (sp?) what. In this case, do you keep the unique mining of underhive or the more vanilla-DF-like masterwork? Not to mention the pretty much everything else. On top of it all, there is the little problem that underhive is a 34.11 mod, which means you got to convert it to the current version.
Abandon hope, ye who tread this path.