Prepare a water bath canner before beginning, and bring it up to 180 degrees F for hot pack canning.
Wash and peel zucchini, then either shred or dice into 1/2 inch cubes.
Bring the zucchini, pineapple juice, lemon juice, and sugar to a simmer in a stock pot. Simmer for 20 minutes (this is not optional, it ensures the zucchini is fully acidified before canning).
Pack the zucchini pineapple into canning jars, leaving 1/2 inch headspace. (Pints or half pints) Seal to finger tight with 2 part canning lids.
Load the jars into a water bath canner and bring the canner up to a full rolling boil.
Process jars in a water bath canner for 15 minutes (below 1,000 feet in elevation), adjusting for altitude. See notes for higher altitudes.
Once the canning time is complete, turn off the heat and allow the canner to cool for 5 minutes before using a jar lifter to remove the jars to cool on a towel on the counter.
After 24 hours, check seals and store any unsealed jars in the refrigerator for immediate use.
Properly canned and sealed jars of zucchini pineapple will maintain peak quality on the pantry shelf for 12 to 18 months.