Considering the double-bond carbons separately, look at the atoms directly attached to each carbon and rank them according to atomic number.

RULE 2

If a decision can't be reached by ranking the first atoms in the substituents, look at the second, third, or fourth atoms away from the double-bond carbons until the first difference is found.

RULE 3

Multiple-bonded atoms are equivalent to their

same number of single-bonded atoms.