R-X can be reduced to R-H by Zn - Cu couple / C2H5OH as a result of:
Electron transfer from the metal to the substrate followed by H+ addition from the solvent
In this particular case the reaction happens as:
The above two steps could be combined as R↷−X+2e−⟶R−+X−
The process happens due to electron transfer by the metal onto the substrate followed by proton transfer from ethanol.
Other methods to carry out reduction are:
a) Zn & Acetic acid; Z and NaOH
b) Zn & HCl
c) Al-Hg (amalgam) in ethanol
d) Red phosphorus and Hydrogen iodide (plus △)
All these methods produce Nascent Hydrogen to facilitate reduction.