The Zone system is "merely" a way of describing the inter-relationships between film speed, subject contrast, exposure, development, film contrast, and onwards to the print.(posted 9744 days ago)There is, IMHO, nothing magical about this system, nor is it the only way to describe what is going on. However, it is reasonably complete. Certainly there are many other methods for "selecting the proper exposure". Cameras with built-in meters use other methods, which can be thought of as cut-down versions of the Zone system.
What the Zone system can give you, even if you use 35mm, is (a) a rigorous way of establishing film speed and development, and (b) a way of thinking about subject luminances, negative density and print density. Armed with this, your pictures will be better, even if you do not laboriously measure shadows and highlights with a spotmeter.