Well Divine Dragon he created, we know his granted wish had limitation, because Zeno erased Zamasu and it seemed Zeno was the only one capable of that. Divine Dragon is awesomely powerful and outside of Zeno who knows if even Grand Priest could do anything to cancel the granted wish and Dragon is only Zalama creation, so Zalama himself should be ridiculously powerful.
In the anime Zen-Oh stated that the Super Dragon could "Do anything. Grant anything", and GP confirmed the same in the manga. So for THOSE caliber of beings to make a statement like that tells you how unbounded the Dragon's wish granting abilities are.
We also know that Beerus was unable to destroy Immortal Zamasu, but Zen-Oh could. So based on that we can infer that Zalama might be somewhere between Beerus-level and Zen-Oh level... But then again, the Dragon is also capable of undoing Zen-Oh's erasure(as seen when it brought back all the universes that were erased during the ToP.) So yeah... Dunno.
If the Dragon's power is even a remote reflection of Zalama's power, then he could very well be Zen-Oh tier.
"I am tired of Earth. These people.
I am tired of being caught in the tangle of their lives."