AFAIK Most of the Ethiopian Commodities in medieval times (at least after the restoration of the Solomonic Dynasty but probably before that too) had three main arteries leading to the coast. One was from Sudan or west Gonder through Gonder/begemeder Proper (North of Lake Tana) and then through Lasta and finally heading to Massawa, the other was from the North but closer to central Ethiopia (f.e. South and west of Lasta) through Shewa and finally heading to Zeila, and the last one was from the southern Tributaries/periphery of the empire (like Hadya and Damot) through Shewa and finally again heading to Zeila. These are the ones that I can recall, now I'm not sure about want went through to Mogadishu, maybe this has something to do with the Ajuran state importing gold that goes through the Northern trade route and then redirects via shewa, but I would have guessed it would go to zeila and then to Mogadishu, instead of directly going to Mogadishu, in return the state would export gums and resins? I haven't read much about the Ajuran, but this is a possibility I guess, maybe you probably know more about it?