No, you can't trade between Diamond and Ruby, but you can transfer Pokemon from Ruby to Diamond after you've beaten the elite four on Diamond, but unfortunately, you can't transfer back, so really think about it before you try to.
trade from them
if you mean can you get Pokemon from pearl and diamond and trade them to ruby so you can get diamond and pearl Pokemon on ruby. then no you can not. but you can migrate ruby Pokemon. you put the Pokemon in ruby that you want to put on diamond or pearl in the PC. save it turn off. then go to diamond and migrate them. must be in ds at the same time. pal park.
you can send Pokemon from diamond to white, but not vice versa. its kinda like with diamond and ruby/sapphire/emerald. hope this helps :D
You have to trade it from either Ruby, Sapphire, or Emerald.
Trade them in from Ruby/Sapphire/Emerald.
Yes. Transfer it from Ruby, Sapphire, Emerald. or Trade it from SoulSilver.
trade it over from emerald or ruby and Sapphire
No, you can only find it on Ruby, Sapphire and Emerald unless you trade it onto Diamond.
you can't catch a rayqauayza in diamond but you can take it from a trade,wfc and ruby,saphire and emerald
NO
You can't get the Regi's in Pokemon Diamond And Pearl. You have to trade from Pokemon Ruby, Sapphire, and Emerald.
Migrate from Emerald, sapphire, ruby, or trade with heartgold and soulsilver