Brett

No she's not. On her best day she's not even close to the power level of Dr Fate. Zatanna has to cast a spell by saying words to do magic. Fate doesn't s/he only needs to think. Fate speaks spells to cast more powerful spells but not the majority. Zatanna is mortal Fate isn't. All of Gates hosts have been altered by Nabu to not age or experience human illness. Without any artifacts of Power Dr Fate is still a class 100 strength with invulnerable body who has high levels of TP, TK, precognition, energy manipulation and flight. When you add the helm, amulet he also gains the powers of matter manipulation, projection creation (like a GL) high level magic and reality manipulation. His TK while wearing the helm is so strong that in an issue of more fun comics he casually mentally pushed a planet into its Sun. In the pages of his backup in Flash during a battle with a lord of chaos the whole world was destroyed (all life on earth) he grew to the point he was standing on a pebble reached out and recreated all life on earth. Inza Nelson Fate had fears more powerful than Zee and she's one of the weakest versions

Your incorrect about Zatanna starting out as only controlling earth wind water and fire. She started hour doing all magic like currently. During the satellite era JLA around the time Reddy was going a little nuts because the tornado champion was remembering who and what he was Zee used too much power in a short time and as such had to limit herself to elemental magic so as to not be destroyed by the magic. Eventually she healed enough to be able to do all magic again.

That is her weakness and the weakness of all DC mortal mages. Using too much power through a single life force in too short a time destroys the life source. To avoid this it's better when using vast power to use it through either an immortal, a talisman, invoking it from a higher power, or through a familiar (more spread across several life forces).

This is why the Spectre is so powerful it's a dead man using the power with no life force to harm. Dr Fate has every host altered by Nabu to be immortal, uses talismans and calls on power invoking one of the lords of order.

The Phantom Stranger has never been a full JLA member only an Honorary one. He also has a mandate to not interfere in the ways of mortals. He's meant to be there only to help a mortal choose their path in their darkest hour. His mini series of 1987 saw him stripped of his power because he chose to interfere rather than just guide mankind.