bash-4.2$ ls -A
x.c  x.cc  x.Cc  .x.(c\|C\|cc\|CC\|h\|H)  x.h  x.hc
x.C  x.cC  x.CC  x.ch                     x.H  x.hh

bash-4.2$ find . -regex '.*\.\(c\|C\|cc\|CC\|h\|H\)'
./x.C
./x.H
./x.c
./x.h
./x.CC
./x.cc

bash-4.2$ find . -name '.*\.\(c\|C\|cc\|CC\|h\|H\)'
./.x.(c|C|cc|CC|h|H)