In PowerPoint, click the box "use presenter view" (which is the next to the last section on your ribbon, under "monitor")
Then click "Slideshow" / and "From Beginning" and THEN you will see (hover near the bottom of your first slide) a circle with three little dots, near the bottom of your first slide. Click that circle with three little dots, then click "show presenter view" / THEN what's on the left (the larger window) will be what your audience sees in your screen share.
(unless you are sharing your entire desktop) / But just a regular screenshare will show only the larger slide, your notes and the next slide coming up will be in the smaller window on the right of the screen. I had to set up two laptops to check to be sure that's what my zoom participants would see!