Is it permissible to work for a Spanish company specializing in the manufacture of women's underwear as an electrical engineer?

There is no objection to working for the aforementioned company in the manufacture of underwear, because it is not intended for ostentation, and it is not something the wearer usually relies on or appears in public with. As for the manufacture of women's clothing that exposes 'awrat (parts of the body that must be covered), that requires further elaboration.