sed output with numbers

I get the same value "chinchwad" for the following 3 statements.

echo "ABCDchinchwad18-Mar-2010-11.sql.zip" | sed -r 's/([A-Z]+)([a-z]+)(.*)/\2/'
echo "ABCDchinchwadII18-Mar-2010-11.sql.zip" | sed -r 's/([A-Z]+)([a-z]+)(.*)/\2/'
echo "ABCDchinchwad918-Mar-2010-11.sql.zip" | sed -r 's/([A-Z]+)([a-z]+)(.*)/\2/'

I expect:
chinchwad
chinchwadII
chinchwad9

The "ABCD" and the text after date "18-Mar" needs to be removed.

echo ABCDchinchwad918-Mar-2010-11.sql.zip |
  LC_COLLATE=C sed -r 's/^[A-Z]*([^-]*)[0-9]{2,}-.*/\1/'

If you get errors with the solution of radoulov (I do on a HP-UX) you can try:

sed 's/^[A-Z]*\([^-]*\)..-.*/\1/'

Yes, I used the non-standard r option and re-interval only because the OP seems to be using the GNU sed (or ssed?).

O yes, you're right, he seems to be using GNU sed.

Regards