20 minutes a day: Should I prioritize vocabulary or noun class drill?

Between work and commute, I only have 20 minutes to study Zulu daily. I’ve been bouncing between three different apps and honestly, I don't feel like I'm making progress. Should I cut out the apps and focus on building sentences with a single grammar focus, or am I better off using that brief time for daily vocabulary exposure? I need a more efficient workflow to feel like my limited time is actually counting toward real progress.