I'm not sure I can describe it a whole lot better than the walkthrough, but I can try. Here is what the walkthrough says:
Drag the cyan/arch pellet to the blue/dotted shard.
Drag the red/circle pellet to the floating cyan/arch shard.
Drag the newly formed cyan/arch pellet to the green/claw shard.
Drag the newly formed green/claw pellet to the yellow/z shard.
Lastly, drag the blue/dotted pellet to the green/claw shard to turn it cyan/arched. A secret door will open to D4.
Just to be clear, cyan = light blue. The way colors are described here is color/symbol (e.g. cyan/arch), but if that's too confusing, ignore the symbol part. Also, it should be noted that you need to first clear the yellow variant of this puzzle to be able to clear the cyan one. It should be a lot clearer when in game as well.
If you tell me which part of this you don't get, I can try to explain it further!
