If $A_1$ and $A_2$ are orthogonal latin squares of order $n$ and $B_1$ and $B_2$ are orthogonal latin squares of order $m$ then the latin squares $A_1 \times B_1$ and $A_2 \times B_2$ are orthogonal.
It seems that this statement is related to quasi-groups but I don't know how...
multiplication of latin squares are described here in the "tensor product of linear maps" section.