Are malasadas and paczki synonymous?

Yes, I would consider them synonyms for Doughnuts.

A malasada (or malassada) is a Portuguese confection related to the doughnut. They were first made by inhabitants of São Miguel, an island of the Azores. Malasadas are made of egg-sized balls of yeast dough that are deep-fried in oil and coated with granulated sugar. Traditional malasadas contain neither holes nor fillings, but some varieties of malasadas are filled with flavored cream or other fillings.
http://www.answers.com/topic/malasada

Paczki are traditional Polish doughnuts. A paczek is a deep-fried piece of dough shaped into a flattened sphere and filled with jam or other sweet filling. A traditional filling is marmalade made from fried rose buds. Fresh paczki are usually covered with powdered sugar, icing or bits of fried orange zest.
http://www.poloniamusic.com/paczkiday.html