I hated Zapdos... it was such a pain and kept parylizing me.
If you want to write Pokeballs or Greatballs or something, do it as one word. It works. ^_^
If you want to refer to a group of different balls* then call them Pokeballs. We'll know what you mean. E.g:
I bought several different kinds of Pokeballs to catch Greevil's Pokemon Waaargh! I was smart again... I'm too scary...
* The star is just there to prevent it being censored...