Even if you have a lab develop your film, you can make use of the principles of the zone system in a modified way. If you're developing your own film (and developing your own film is not difficult or costly, and does not even require a dedicated darkroom), you would first test for film speed with your system and film/developer combination, and then you would test to see how much variation in development time you would need to effect predictable adjustments in contrast, and then over time, you might fine tune those results to your print method and tastes and to account for the small variations in film speed that are associated with adjustments in development time.
If a lab is developing your film for you, you can still do a film speed test in the same way you would, if you had developed it yourself. You can do this with a densitometer, or you can ask the lab to print contact sheets for you at the minimum exposure for maximum black, and determine visually what film speed gives you adequate shadow detail.
While you can't usually do things like figuring how much you need to adjust development time to get a 1 or 2 zone expansion or a 1 or 2 zone contraction of contrast, you can ask the question in reverse--"If I tell the lab to push one or two or three stops or to pull one or two stops while I actually keep my film speed constant, how much of an expansion or reduction of contrast will I get?" What the lab is calling a "push" or a "pull" is really just an extension or reduction in development time, and it does not change the film speed substantially--only the contrast. You might find, for instance, that what the lab calls a 1-stop push corresponds to +1, and maybe a 2 stop push corresponds to +1.5, and a three stop push corresponds to +2.3, or something in that ballpark, or maybe the lab habitually overdevelops and "normal" development is really +.5 (a common situation). The point is that you can still expose for the shadows and develop for the highlights with negative film, as long as you run a few tests to know how to control these factors.
This does not mean constant testing unless you are constantly trying new materials. Find what works, and stick with it.