Complex sentence: In 1874-75, the Egyptians obtained a "firman" from the Ottomans by which Zeila fell under Egyptian rule, while at the same time securing British recognition of her jurisdiction as far east as Cape Guardafui.
Split into simpler sentences: In 1874-75, the Egyptians obtained a "firman" from the Ottomans by which they secured claims over the city. At the same time, the Egyptians received British recognition of their nominal jurisdiction as far east as Cape Guardafui.