"Studies on DMSA and Zinc showed DMSA did not raise zinc excretion in the urine to any significant amount (though it did very slightly"

My concern isn't so much for the amount of zinc lost during chelation, but that since DMSA does chelate zinc to some degree, extra zinc in the blood during chelation might cause more DMSA to be used up grabbing zinc, rather than grabbing toxic metals. While the percentage of zinc in the body that is lost is low, but an even slight increase in the amount of DMSA used up grabbing zinc rather than toxic metals wouldn't be good.

As for vitamin c, even 500 mg a day is a megadose, but over 2 grams a day is an ultra megadose.