[(L1[i] + L2[i]) for i in range(min(len(L1), len(L2)))]
[(x + L2[i]) for i, x in enumerate(L1)]
Lx, Ly = ((L2, L1), (L1, L2))[len(L1) <= len(L2)]
[(x + Ly[i]) for i, x in enumerate(Lx)]
How to zip two lists of lists in Python?