Hey, I'm on The Zolazin Battle and have completed it 2 out of 3. I have more than enough Zolazin debris, should I sit on it and rack up ZD? Also, is this the only time I can do this?

I believe the Zolazin Battle's the only mission in which you have a chance of getting Zolazin debris, so if you plan on collecting it then that'll be your only chance

As for "camping"... depends on how quickly do you want to finish the mission chain

Camping is a good idea if you are after the extra artifact drops to sell them. There is only one other mission I wished I had camped on. The Drannik Extinction is a good one to leave open if you want to fast rank.
The kill shot on the Drannik Archivist NPC is worth 86xp; by far the highest return rate for the easy kill.
Although the data chips can't be traded or sold, you can eventually spend them in the mission. You can then create your own Gaia planets or you can sell your Gaia seed services. It is a win/ win all the way around.

Many high levels camp on Decrypting the Vault. 6 shot NPC that gives 200 RP, 50 exp and an artie you can sell.

ODragon, how much can you sell the arti for? I'm on that mission.

It's a scrap sell artifact. You can't sell it to other people. The scrap value is 29k-116k credits each.

some mission npcs are worth camping their mission in, like RDA and Drannik Archivists for research, exp, etc.

Others no so much. For me, those would be Iso-Runners.