I would like to book a flight from MUC to SEZ via AUH on EY, all on EY metal, all in Y. Theoretically, this route is bookable through AB's website. In practice I had to reserve it through a TA, though, as the combination of the particular flights is not offered by the websites.
which specifiy combination is not possible? Usually AUH-SEZ is done on A332 HM-metal, however, there are 3 AUH-SEZ flights (1-3-5--) operated by EY A320 (you have to fly (-2-4--7 overnight out of MUC). I had no problem booking this on AB-code (AB4004, AB4064, AB4065, AB4008) through airberlin.com
Also the HM-operated flights have AB-codeshares.