Enzo will carry on at light heavy where he left off at cruiserweight, and Cleverly would give him a rather humiliating beating. Enzo has said himself it's his fighting style that has got him knocked out in the past, and I really don't see him doing things differently now.
Unless we discover that Enzo was actually a podgy Light Heavyweight that wasn't really taking things as seriously as he should, I think he would quickly start to appear the less sharp of the two (and probably would regardless at this stage). It would be like when Chris Byrd fought that bloke whose name I can't remember when he dropped to LH. Chris who had previously looked like having reasonable reactions and timing whilst at HW, suddenly looked about 10 years older with terrible timing and reactions. If I had to bet on it, I would say that is a far more likely outcome than Enzo suddenly finding his right weight, it's too late in his career for something like this. While Enzo would still have the power advantage, if Clev is able to take shots that don't land cleanly, then I think the advantages of not being totally shot would make themselves very clear. That said, Enzo has for the most part only lost to big cruisers with a good punch (or in Ola's case, one with excellent defence), he's tall at 6'4" and has never lost to anyone lighter than him. Enzo has a chance, but it is the typical puncher's one.
Chris Byrd fought a mediocre LHW name Shaun George and lost. Funny you bring it up, because thats exactly what came to my mind when I saw this thread.
I think Enzo should take a different route, win a world title then have a battle of Wales with 2 titles on the line. Both would beat Bellew as he is ****, domestic fighter only!! The Danny Williams of the light heavies!!