I think the only trick is having a unit that can take out the sword infantry in the upper right and counter-kill (or at least survive) the mage's counterattack, since after that every other foe comes south into meat grinder territory.
I went with Flier Emblem (Bunnymilla, Hinoka, Clair) and Reinhardt. Bunnymilla blows up the red sword in the upper-right, green cavalry mage pokes her and she swats him down too. Everything after that is cake.