I think I remember an earlier issue that someone had with the OR operand not quite working as expected.
But since all my forum posts were purged at some point I cannot find it.
I believe that the || operand(s) behaved like an AND instead of an OR despite being defined as such.
It was pretty weird.
Perhaps try AND or && ?¿?
Sadly the operand "AND" instead of "OR" didn't work either. Perhaps what I want isn't possible in 1.7.10. If you know of any other options to make mobs despawn instantly at a specific time of day, I'm open to suggestions!