- Epoxide gets opened at the least hindered side by the ethoxide (acting as a nucleophile rather than as a base in this case).
- The resulting alkoxide intermediate can itself act as a nucleophile. In the middle intermediate could either kick out ethoxide (which would give back the starting material), or kick out the chloride (to give a different epoxide). Since the chloride is a better leaving group, it is this one that probably leaves (theres an element to which the whole thing is reversible away, and if it does kick out ethoxide, the ethoxide can just attack again to re-form the middle alkoxide intermediate)
The product on the right hand side is probably what the mixture would converge upon, given that chloride is a better leaving group than ethoxide.