Learn German: Unsere Katze ist sowohl zahm als auch gehorsam.

It translates to "both ... and". Here, it connects two equal parts of the sentence—the adjectives zahm and gehorsam—to emphasize that the cat has both of these qualities. Because it is a coordinating conjunction, it does not change the word order of the sentence.

I expected "and" to be translated as und. Can I say sowohl zahm und gehorsam?

No, that is a very common trap for English speakers! The phrase for "both ... and" in German is a fixed pair: sowohl ... als auch. You cannot swap out als auch for und.

Is it a typo that there is no comma before als auch?

Not a typo! Even though German uses commas more often than English, you generally do not put a comma before als auch when it simply connects words or short phrases like these two adjectives.

Why don't the adjectives zahm and gehorsam have endings, like zahme?

Because they are separated from the noun by the verb ist. When adjectives describe a noun but come after a "to be" verb (these are called predicate adjectives), they keep their basic dictionary form and never take an ending. You would only add an ending if they were right in front of the noun, as in unsere zahme Katze (our tame cat).