While Doom no longer has the raw power he had as Apprentice to the MoD. I'm fairly certain the knowledge was never removed. Realistically speaking that event alone should put Doom over just about any other sorceror. He's had millenia to learn all about destruction and magic. That said on a random encounter I'll give it to Zatanna if it was purely magic. Her on the fly magic is more versatile imo. Doom has a tendency to go blasty magic when he's not prepped for an encounter. Zatanna could say
Nommus S'mood ssenkaew.
Squirrel girl appears and Doom surrenders. Point is I'll give Zatanna an edge on the on the fly magic but the tech and physical capability + general defenses Doom has in place+ any countermagics he can and would perform off hand gives it to him 6-7/10