What pickled yellow-green vegetable is this, in Chiu Chow Garden's appetizer?

I think that is daikon, which has many names including several that include the word "radish".

There are a couple of vegetables in there that are yellow-green, one is a leafy vegetable, which is likely some variant of Chinese cabbage/Wong-Bok/Napa cabbage. This part will have the classic ribbed stems and pale leafy parts seen with these vegetables. This is the same cabbage used in many Kimchi recipes, though these can also contain a bunch of other vegetables too.

The larger cube shaped pieces are likely to be, as @LSchoon noted, Daikon (lo-pak/lobak in Cantonese or Luobo in Mandarin). If this is the case, they will have (if you can piece together a ring made out of them) an outer layer that is less transparent than the middle, and radial rays that seem to emanate from the center of the daikon - you can see them in the picture associated with this recipe.