Fired Ohio State assistant coach Zach Smith just broke his silence on his alleged domestic violence ... saying he NEVER beat his ex-wife.
Zach went on 105.7 The Zone to tell his side of the story ... and says while he was in a "volatile relationship" -- he "never committed domestic abuse against her."
As for the photos Zach's ex wife Courtney Smith released showing bruises on her body from the alleged abuse ... Zach said he may have caused them while "restraining her" but insists he never struck her.
Smith also says PLENTY of people at Ohio State knew of the accusations back in 2015 .