Sacrifices that are close to the victim's heart are necessary for the Eclipse and it was made apparent to Zodd that Guts meant enough to Griffith that he'd lead his men on a search and rescue mission whilst going directly into battle against the apostle just to save Guts. That probably made Zodd realise how necessary Guts would be.
As for the alternative scenario of the Eclipse, it's hard to say. If most of the Hawks are slaughtered in battle, or at least the major ones, Griffith may not have the necessary sacrifices to become Femto or may not be in the state of mind to sacrifice more for his dream when it's apparent Guts was special to him and this was before his torture and seeing the bond between Casca and Guts affected him. Given causality is a major part of Berserk, he'd probably still become Femto somehow, likely being able to escape with his remaining soldiers, form a new Band of the Hawk and probably go through the Eclipse afterwards. It's stated that the Eclipse occurs every 216 years, so the Battle of Doldrey would still be too early for Griffith to realise his destiny.