Let Z be Zaki's age. Oscar's age now is Z/2. Two years ago, Oscar's age was Z/2-2.
Two years ago: Z-2=3(Z/2-2)=3Z/2-6.
Therefore, 6-2=3Z/2-Z=Z/2, so Z/2=4 and Zaki is 8 years old, so Oscar is 4 years old.
Two years ago Zaki was 6 years old and Oscar was 2 years old.