*non-isomorphic*to the other groups defined by the list.

The groups are certainly the same order...

I understand that 6) $$Z_8 \oplus Z_3 \oplus Z_{25}$$ is a black sheep because it is the only cyclic group (gcd of the m's is 1).

But what about the others? How do we know that they are mutually non-isomorphic?

btw, to write the above in tex, alls I typed was Z_8 \oplus Z_3 \oplus Z_{25}