ZERO HOUR was DC’s 1994 crossover event that aimed to streamline the many and varied future and alternate timelines in the DCU at the time, in much the same way CRISIS ON INFINITE EARTHS had handled the Multiverse. Parallax – at that point the former Green Lantern Hal Jordan – attempted to recreate the universe, using the opportunity to correct mistakes he and others had made.
DC produced a teaser or ashcan sampler before ZERO HOUR hit the stands as well as a sampler for the Zero Month that followed the event.
You can see both on this page.
ZERO HOUR was collected in both paperback and hardback – you can find some short notes on them here.
A New Earth-2?
In October 2016, the CBR website published another in their long line of articles dealing with comic legends, this one titled ““ZERO HOUR” was originally going to end with the Justice Society of America on their own separate Earth.“
You can read the full article here (scroll down past the Silver Surfer story) but this quote from ZERO HOUR writer Dan Jurgens sums it up:
What would have happened if the Hal Jordan/ Parallax character create other Earths, I wanted one Earth to survive to put the JSA on, and give them back Earth-2. If you had that separation, they would always have a place to be where time could exist on its own, and they could exist with the DC Universe.
As with all other DC events, a number of house ads ran in other titles in the run-up to ZERO HOUR‘s publication.
Here’s a short page with what I’ve found.