regex search string for A and B or C but not D -

i'm new regex. i'm using "everything" search utility supports regex , need simple search. need find files on computer have both th= , db= in names (btw not regular names character strings) , files have ch= need exclude files have el=. example, need find files named xyz=th=db=, ch=xyz=, db=th=, etc. not th=xyz=, xyz=db=, el=th=db=, ch=el=, etc. in advance help.

you want lookaround:

http://www.regular-expressions.info/lookaround.html

baiscally can find this:

/(a|b)(?!c)/ 

and matches or b unless either 1 followed c.

if regex engine doesn't support 0 width assertions gets harder kind of thing.