I was at JS Cambridge presenting and whilst it was a wonderful meetup the projector was tiny and a bit blurry. It was the first time I have ever really needed to zoom my screen in PowerPoint.
In Windows to zoom PowerPoint you just pinch and zoom the touch screen, but on Mac, PowerPoint doesn't have the same feature, there is no keyboard or touch pad feature to emulate it at all.
Accessibility to the rescue.
Luckily on Macs once you enable the feature you can just press control + a two finger swipe up to zoom the entire screen.
To enable the feature Go to System Preferences > Accessibility > Zoom and make sure Use scroll gesture with modifier keys to zoom is ticked.
Now you can zoom in and out of your screen to your hearts content. You might want to practice a bit if you plan to use presenter mode however.