SPL has more adjustment range and much better track record of reliability, plus easy on-car adjustment. Its not even a question - SPL is the best option. Dont cheap out
You also need either the toe arm for true type coilover or midlinks for OEM type
Z1 has documented- self admitted manufacturing issues for at least one run
Don't believe me? Read yourself
Z1 front adjustable camber arms
Oh, and the Z1's aren't adjustable on car. Gotta take 'em off. Oops
we always recommend SPL because they are the best