One is a mythical one-eyed monster, and one you feed your fish.
But seriously, I think I have seen some fish food labeled as "cyclops" and to me that just means it's probably the same stuff as "Cyclopeeze", but isn't from the manufacturer that has the trademark on the name. So if they used the name, they'd be infringing on their trademark and would probably be sued.
The quick answer to your question fijiwigi is that it all depends on particle size of the food, and what the food consists of - animal or vegetable. Zooplankton are large particles (relatively) of mostly animal based stuff, while phytoplankton are smaller particles of mostly plant-based stuff, but with other dissolved organics too.
I think if you do some searching for the various terms on Google, you'll find enough definitions and explanations to make your head swim. And there's a really good chapter about coral foods in Borneman's book "Aquarium Corals" too. (Hint, hint.)
PS... Cyclopeeze are tiny "micro crustaceans" that are harvested from some pristine arctic lake, that have higher than normal nutritional value for something so small. More info here...
CYCLOP-EEZE®: Product Info
I use it - a little goes a long way. Fish seem to love it.