Here I go repeating myself again, gag me.
I like
Zack, I really do, more than the actual name
Zachary.
BUT if I were to name a boy
Zachary I would probably call him Zooey. I know I know, most parents wouldn't dream of it since
Zoe has been SO popular for girls, but I first came across Zooey in the JD Salinger story "Franny & Zooey" and there Zooey is a boy, and it is a NN for
Zachary.
I fully understand your hesitations though, different in an irritating way, the "oh... Zack..right". This is a big headache for me with trying to find a good balance between English and Swedish names. After all one doesn't want the name to become a constant issue.