Why is query using Clustered Index when it shouldn't?
The "like '%zzz%'" largely negates the possible benefit of the index since it will need to examine each entry to determine whether it matches; and doing the "SELECT *" means it would have to do a lookup to the clustered index to get all of the column data on the matched records; the optimizer can't estimate how many matches there will be so chooses the clustered index. 

Try changing it to "like 'zz%'" and see what you get.