In a medium saucepan, bring water and sugar to a simmer over medium high heat until sugar is dissolved.
In a food processor, puree pineapple with its juice until smooth. Transfer to a metal bowl, and stir in syrup, lemon juice, orange juice, and orange zest. Freeze until slightly firm, but not frozen.
Process mixture again in the food processor or beat with an electric mixer until smooth. Transfer to a freezer container and freeze until firm, about 2 hours.
