Well, Zoro and Sanji are warlords lvl, so you can compare them to Kage. But then again, we saw the defeat of both of them, which is why even now, just their defeat wouldn't be enough to make Imu's hype level comparable to Madara. He needs to do more than that.
But, if we use Madara's Meteor summoning, Imu already did that...still, we thought it was technology. If Imu will use this power and show us that it was his powers(even tech-related), then it will be equal to Madara's meteor: