The smaller item is Brass and looks very much like a Magazine for a No 250 or 251 fuze as fitted to the 40 mm Bofors High Explosive shell-are you certain they are all empty as they are very powerful when filled-even partially!
No idea about the plug type item.
Brass can be very nicely cleaned sympathetically by simply leaving it in household vinegar for many hours, just keep cheking it every few hours to make sure nothing untoward if occuring.
Zinc or Maizac metal is a big problem to clean as it is such rubbish and is often porous due to poor casting/pressure injecting etc.
Good luck with the collection and you have a very nice start with your items-remember primers are usually the "missing part" case collectors are looking for.