Great to see You back!
Yeah I think it does need efforts to make a clear defined limit especially with DC diverse magic systems. Nevertheless I think it would be great to see have some limitations to Zatanna as long as she written as competent and active fighter. But how do You clearly define it? I mean even movie Dr. Strange can do a lot of things, the first movie is quite grounded tho.
Would 80s Zatanna where She can only control 4 nature elements is a good basis? The backward speech is her way to cut mana cost by commanding the energy around. She can use other way of magic like hand waving for a quick reaction albeit with higher cost. I think the activation of Homo Magi Medulla Jewel could be a clear mark of Zee character progression as she become more knowledgable skillful and powerful