Hi uptownsleeper,
There is more about zoning in this article and more detailed information in post #11 here and post #2 here.
Latex is very point elastic and also has a high compression modulus (it gets firmer faster than other types of foam when you sink into it more deeply so it’s more “supportive” even in softer versions) so it’s much more likely that a non zoned latex mattress will work well even for those that may benefit from zoning with other types of mattresses or materials (see post #7 here)
The effectiveness of zoning depends on how well a specific zoning pattern matches the body type and sleeping positions of the person in terms of PPP. Some types of zoning can be helpful with some people and some can be detrimental and the only effective way to know whether a specific zoning system is effective for a particular person would be based on their own personal experience but it can certainly be helpful in some situations and for some people yes.
There are some suggestions in post #2 here that may be helpful with a new mattress that is too firm but if you need some additional softness and pressure relief on your mattress then a topper can certainly be a good solution. The key with a topper is to add “just enough” thickness and softness so that in combination with the mattress it will relieve your pressure points in your most pressure prone position (generally side sleeping) so that there is less alignment risk in your other sleeping positions.
If you do decide to add a topper then post #2 here and the topper guidelines it links to can help you use your sleeping experience as a reference point and guideline to help you choose a topper that has the best chance of success and also includes some links to some good sources for toppers as well.
Phoenix