See the image.
Work Step by Step
-- To determine if a structure is an E or Z isomer, we need to first pick the group with the higher priority on each of the two carbons connected with the double bond. -- To pick the group with the higher priority, we can do the following atom connectivity analysis as shown by the image below. Let's examine the first atom away from the double bond. The group in which the first atom has the higher weight has the higher priority. If the first atoms are the same, we keep examining the 2nd, 3rd... atom(s) away from the double bond. As soon as we find the group in which the Nth atoms have greater number of the type of atom with the highest weight, we can determine that group has the higher priority. And if an atom is connected to another atom with multiple bond (double or triple), it is treated as that atom being connected to another atom for the same number of single bonds. -- Finally, if the two picked groups with higher priority are on the same side, the structure is a Z isomer. If they are on different side, it's an E isomer.