I don't think Zavala is jealous of us. Proud of us more than anything, but I doubt he's jealous. The guy's is just weary and depressed from years of work and stress, and we know it's been really getting to him over the last 3 years. I think what is more likely is that Zavala will scold us for using Stasis because it's an unknown power from our biggest enemy, but eventually resign from his initial thoughts over time either by watching us control it, or by him eventually realizing that Light alone isn't enough to defeat our enemies.