I used Rotella as well. A zinc additive might be a good option for the first one too
Joe Gibbs br oil
The zinc isn't really as necessary on our engines since we have roller lifters. It is more critical on a flat tappet style lifter like an old small block or a Cummins. Without a zinc additive it is easy to flatten the lobes on the cam without the extra cushioning it provides. It's still not a bad idea, but I've never really worried too much about it on a Duramax.