Steve's diamond armor during the later moments of A Minecraft Movie was a great little reference, and this is how it compares ...

legs:{id:diamond_leggings,count:1},feet:{id:diamond_boots,count:1}}} If you want to summon any other mob with these armor parts, you can change the mob's name in the command line. If you want the ...

and the items are a diamond helmet, chestplate, leggings, and boots. If you want, you can change the type of mob into any other that can wear armor, like skeletons, zombified piglins, piglins ...