Well the normal thing is you apply the same shader to every material zone. It doesn't matter that they are different groups of polygons.

On the other hand, you could use the group tool to assign the same material zone to all the groups. Then you only have one shader to modify.

Open the group tool. Select each existing group one by one. For each, assign material to the same name. It can be an existing mat zone, or a new one you make up.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)