Hi madinsomniax,
You can see my comments about zoning in this article and in post #11 here. A latex core that has a relatively small difference between the zones can still be “somewhat helpful” but you may not “feel” much difference between a zoned layer and a non zoned layer that has the same ILD as the softer parts of the zone (the upper and lower third for example) when you first lie on the mattress (most of the initial feel and pressure relief of a mattress comes from the upper layers) … but if the zoning helps keep you in better alignment over the course of the night it can certainly make a difference in how you feel when you wake up in the morning.
While it may not “feel” like it because there are so many subjective elements involved with “feel” … a quilted cover over a softer layer of latex will tend to reduce the amount you will sink in to the latex … not make it softer. Of course it may affect your shoulders more than your hips so it may “feel” like your hips are sinking in more relative to your shoulders.
It would be helpful to describe the specific symptoms you are experiencing in much more detail and whether they seem to be connected to pressure issues or alignment issues (see post #6 here). What you are describing about how far you are sinking in is a more subjective description “about” your experience but without more specifics about the actual symptoms you are experiencing it is difficult to make any meaningful suggestions.
Post #2 here and the posts it links to has more information about the more common symptoms that people may experience on a mattress that can also help with the detective work or the trial and error that may be necessary in deciding on any fine tuning or the combination of materials that may work best for you.
Phoenix