Someone is paying zinke under the table.
I think that he is playing two games. It all goes down to local politics.
He immediately announced that the Upper Missouri River Breaks National Monument in his home state of Montana would be spared. It is very popular among Montana sportsmen and, if he decides to go back to Montana and run for Governor or the Senate, it would be remembered by the voters in a state that treasures its hunting and fishing.
The ones in his sights are those in states with Republican congressmen and senators who opposed the monument designation. Utah's Republican congressional delegates are unanimously opposed to the size of all three of the national monuments slated for review in their state. I suspect that all them will be "adjusted".
Here in New Mexico, Zinke is leaving the Rio Grande del Norte monument alone, probably because our only Republican congressman Steve Pearce, here in southern New Mexico, has announced that he is running for Governor. Northern New Mexico is largely Hispanic and Liberal, and Pearce can't afford to antagonize them any more than they already are. Southern New Mexico is Pearce's stronghold, so he probably believes that he can get away with having the Organ Mountains and Desert Peaks monument in his district radically downsized and get back at most of his political opponents in the process. Independent polls showed local support for OMDP at anywhere from 68% favorable to 83% favorable, but he pretty much ignores Dona Ana County as a lost cause, and I think that he figures that he can win without them.