Energia-2 was a fully resuseable, fly back version of Energia. The Zenit boosters for Energia were always reuseable, returning to earth by parachute but Energia-2 also involved a reuseable flyback core booster, thereby allowing the whole rocket system to be recovered. Indeed, the Zenit Boosters could also be be given flyback capability in addition.
Below is an illustration from the www.buran.ru web site that shows how Energia-2 would work. The main booster would make a normal landing back on Earth in the same way the Space Shuttles do.
Above: Energia-2, this view cleary shows the main flyback booster, as well as the four Zenith side boosters.
Above: Artistís impression of Energia-2.