require 'zip'

Zip::File.open('b.zip') do |io|
  io.each do |entry|
    puts "Entry: #{entry.name}"
  end
end

# output:
# Entry: 1_factura_14277089822133838.pdf
# Entry: B632761741427708982713.pdf
# Entry: factura_14277089822133838.xsig
# Entry: RespuestaWS.xml

Zip::InputStream.open(StringIO.new(File.read('b.zip'))) do |io|
  while (entry = io.get_next_entry)
    puts "Entry: #{entry.name}"
  end
end

# output:
# Entry: 1_factura_14277089822133838.pdf