In a large stockpot, bring the zucchini and sugar to a boil. Boil and stir constantly for 6 minutes. Add the lemon juice and pineapple; cook and stir for 8 minutes. Add gelatin; stir for 1 minute. Remove from the heat. Skim off any foam; fill jars or plastic containers. Cool before covering with lids. Refrigerate up to 3 weeks.