particle と - Why is there a と in front of 別?

I found this sentence in a workbook:

それとこれとは別でしょう。

My translation of this sentence is:

As for that and this, they are different.

What is the significance of the second と? How is the sentence translated with it?

Answer

Originally, と was used after each word in a list. From here:

いくつかの事柄を列挙する意を表す。「君―ぼく―の仲」
[補説] 並立する語ごとに「と」を用いるのが本来の用法であるが、現代語ではいちばんあとにくる「と」を省略するのが普通となっている。

The last と in a list is usually omitted at least in modern Japanese. In this sentence, you can safely omit the second と, but explicitly putting the second と emphasizes that these two (それ and これ) are contrasted. AとBと is still common in formal or complex sentences.

See: 「X」と「Y」と - how does the second と affect the sentence?