Learn Polish: Ten krój jest piękny, zwłaszcza dla wysokich kobiet. - This cut is beautiful, especially for tall women.

Yes, they are almost completely interchangeable here. Both mean "especially" or "particularly." Zwłaszcza often feels like it's pointing out a specific, notable subset, while szczególnie focuses slightly more on the intensity of the trait. In everyday speech, replacing zwłaszcza with szczególnie here sounds perfectly natural.

Would przede wszystkim work here as well?

It would work grammatically, but it slightly changes the meaning. Przede wszystkim translates closer to "first and foremost" or "above all." If you said przede wszystkim dla wysokich kobiet, it implies the cut was designed primarily for tall women, and others are an afterthought. Zwłaszcza simply means it looks exceptionally good on them.

Does krój only refer to the cut of clothing?

Mostly yes, it is the standard word for the "cut," "style," or "pattern" of garments like a dress or a suit. However, you will also frequently see it used for typefaces and fonts in typography, which is called krój pisma.

I know dla requires the Genitive case, but why doesn't the plural noun kobiet have a typical case ending?