Zoom offers step-by-step instructions for using Microsoft Powerpoint presentations with screen sharing in their Help Center article. You can also refer to these two quick tips:
Dual Screen
If you are screen sharing with Powerpoint and have multiple displays/monitors or on a projector, click Swap Displays in the Powerpoint toolbar to switch to to the presentation screen during Slide Show Mode. 
SlideShow in Full Screen and Chat
If you are using Full Screen presentation mode in Powerpoint, but you want to also use the chat feature in Zoom during your presentation, change the Show Type to Browsed by an individual (window) in the Set Up Slide Show options under the Slide Show menu in Powerpoint