In brief
Small and medium hard zucchini are convenient for a quick dish. Readiness is tracked by texture, not just by the watch.
Useful to know
Choose zucchini with a shiny crust and a hard inside. The University of Iowa recommends small to medium sizes and storage in an envelope in the vegetable compartment of the refrigerator. Rinse before use. [1]
For a frying pan, the source suggests separating the ends, cutting along and then into pieces. Cooking is to soften, but without yielding a kosher texture. [1] This is a more useful criterion than the idea that each zucchini should stand a specific number of minutes.
You can practically cut a batch of close-ups first. When stirring, check a larger and smaller piece, instead of judging only by the thinnest. It is not necessary to change the temperature repeatedly if the different size is the cause of the uneven result.
When choosing a recipe, specify whether you want individual pieces, stuffing, or baking mixture. The appropriate form for one is not automatically the best for the others.
Sources
For further detail and to check the information: