Sorry, my initial instinct was Zachary, but then I would do Zach for short. But I'm always one to ask spelling before I write it, as there is so many ways of spelling names now (learnt this particularly from working in a bank). I had a surname which was always miss spelt (and it was a spell it as you would say it name)...at first it was frustrating but it became no big deal. I would say just point it out everytime they spell it wrong, eventually those people will learnt to ask everyone the spelling of there name (like I learnt to do).