If the Portuguese really manage to occupy the land passage between Soron Lake (Lake Tanganyika) and Lake Malawi, it would indeed have an impact on East Africa because it is a necessary route for the East African Central Railway to enter the interior.
However, the difficulty of occupying this place is quite high. There is the heavy industrial base city of Mbeya in East Africa, three large armament factories, and it's the station of the 111th Division. Lake Malawi is also one of the three major bases of East Africa's River and Lake Team, and the Black Corps in East Africa trains on the eastern shore of Lake Malawi.
All the advantages of water and land transportation are in the hands of East Africa, and logistical supplies are quite convenient. If the Portuguese manage to break through the East African army from Lake Malawi and the coastal areas, then there is no need for East Africa to exist.
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