Hi
It is generally believed that Jacksons do not require much supplementation, compared to panthers or veileds.
Since your chameleon lives outside a lot, and assuming you have UVB lighting inside as well, you do not need a product containing D3. Is it safe to guess that being outside he also eats some wild bugs, prey he catches outsides himself like flies and snails? If he catches a fair bit of wild prey, and if there was improvement to your gutloading, you'd hardly need to supplement at all.
If the chameleon is not eating wild insects in addition to what you are offering, and/or if you dont improve your gutloading, some supplementation will be useful: Use the RepCal herptivte once or twice a month, and use the zoo-med no more than once a month (you dont need the D3 that's in it, but it will provide some preformed vitamin A, which your chameleon may need in small amounts, if it is not eating a wild variety of well gutloaded prey). With Either product, dust LIGHTLY only one or two bugs.
If your chameleon is eating wild bugs, or if you start gutloading well, you could/should use even less supplement.
Are you also dusting occassionally with a phosphorous and vitamin free calicum product?
You can easily improve your gutloading / what you feed your crickets and roaches:
https://www.chameleonforums.com/blogs/sandrachameleon/75-feeder-nutrition-gutloading.html
and dont forget to gutload the mealworms too:
https://www.chameleonforums.com/blogs/sandrachameleon/443-superworm-substrate-gutload-one.html