How can I ask my parents if I can change my last name?

I don't think they would mind that, because you still want to have both last names, so neither of them will be offended. You should just bring it up, I don't know any way you could work around to it lol. I don't expect them to get mad about this, but you might have to explain why you want to do this with more than just that the maiden name sounds cool.

Just tell them you want to do that. This isn't at all uncommon. Actually, in Spanish speaking countries, children take both their father and their mother's name. I even considered it myself, once. I'm Italian, but my paternal grandfather isn't. So I wanted to hyphenate with my mother's maiden name because I didn't like the Anglo Saxon implications of my father's surname.

I don't see how it could be a problem. Your mom's name is your name too. In Hispanic culture it is a tradition to keep your mom's name in exactly the way you wrote! It's unusual but no harm...