It's just an overstuffed (though normal sized) issue of DC Special (#19 of December-January, 1975/1976), with a cover by Ernie Chan....
...and featuring battles of Superman, Green Lantern and Wonder Woman fighting some giant menaces!
Action Comics #343
The Superman Revenge Squad releases the giant android, Eterno, from his underground prison of the element, absorbium (created by an alien race, the Xan), to bedevil Superman in the city of Metropolis, bringing doomsday to where Superman lives. The two powerhouses battle, until Eterno finds out he was manipulated by the Superman Revenge Squad, then he attacks them. Trying to stop him, the Squad makes more absorbium, stopping Eterno (as Eterno stopped them!).
Green Lantern #53
Hal Jordan found himself a new job (after having given up his time as a test pilot), becoming an insurance adjuster, heading up to the site of a crashing meteor. When Hal arrives there, he finds the giant alien, Thotan, who was inhaling Earth's oxygen (with the plans to take the air back to his homeworld). Green Lantern battles the alien, even getting sucked up inside of him, until Hal comes up with the idea of facing his foe on his own terms, using his Power Ring to grow to giant size to face the alien.
Strange Adventures #28
For a time, Earth had few super heroes protecting it, and faced strange, alien menaces, and relied on us tricky humans to protect it from threats from beyond!
There was a little surprise awaiting the people that defeated this monster after all his confused destruction....
Wonder Woman #106
The alien giant Tooroo wanted to impress his girlfriend, the giant Rikkaa, so he got her a charm bracelet...but, it happened to include Wonder Woman, Steve Trevor, Wonder Woman's lasso, tiara and invisible plane! To get free, Wonder Woman challenges the giant to three contests, and, by winning them, is able to get herself, Steve and her belongings returned to Earth (and a pledge that these aliens would leave Earth alone....).