i would spell it Zachary, and probably Zac.

the thing is, if its a stranger spelling the name, they will spell it however.. if it were family/friends/school etc they SHOULD spell it correctly, because they know how it should be spelt.

i get the oddest spelling of Krystal sometimes!! i understand the C or K, but Christell, Cristal, Krystall... and this is family and friends!! argh!
Haha my son Jaidan's father spells his name Jaiden all the time... even to the point where he made him a special cake for his birthday (he is a baker/pastry chef) and he spelt it wrong! I stuck the candle through the e lol