"Latter" when referring to more than one [duplicate]

Solution 1:

I would not use either 'former' or 'latter' when making comparisons between more than two items, just like you should not use 'better' or 'worse' when describing one from many. 'Best' and 'worst' are preferred in that case.

If Alice scores 10 and Jim scores 5, the better student has scored twice as much as the worse. If Bob has also scored 3, then the best student has scored more then three times the worst.

Similarly 'first' and 'last' are preferred when considering order of more than two things.

I would write your sentence as:

The first case can not be compared with the second and the third cases, because the material used in the first is water-based while the material used in the others is oil-based.

I would probably also use a pronoun to avoid repeating 'first', but I leave that as an exercise for the reader.

Solution 2:

I, sometimes, find fine to repeat the same words but shift the order you have to add emphasis. In this case I would say:

The first case can not be compared with the second and the third cases, because, in the first case the material used is water-based, while in the second and third case it is oil-based.