The following is the agreement bewteen CO and QF and is quite clear on endorsements..
I have never had a problem with a ZED tkt made out to QF being used on EK/BA or TG...

"ZED COUPONS ISSUED BY ANY ZED MEMBER CARRIER SHALL BE
ACCEPTED WITHOUT ANY ENDORSEMENT BY ALL ZED MEMBERS
WITH WHOM A COMPARABLE OR LOWER FARE LEVEL HAS BEEN
AGREED, PROVIDED THAT ALL APPLICABLE TAXES ARE PAID BY
THE ELIGIBLE PASS RIDER. CO MUST HAVE A ZED AGREEMENT
WITH A CARRIER IN ORDER FOR A ZED TICKET TO BE ACCEPTED
AND VALID FOR TRAVEL."