Zoom charges a $/user/month. Companies pre-covid had video conferencing platforms. Zoom did a lot of shifting of existing spend from business on Webex & Hangouts/Meet to its platform.
Even if Zoom's average usage per paid user goes down post-pandemic, it's revenue will remain constant and could still grow as new employees are hired and new companies switch over.
The strategic threat for Zoom at this point is big players providing a more integrated offering. Microsoft being the best example.
Zoom was easy for corporations to adopt quickly in the pandemic rush, but companies that already had Webex or others didn't switch.
When a player offers cross-sell discounts with other products they offer and as long as the functionality is 80% as good, they will absolutely go with the cheaper vendor.
Zoom needs to diversify to stay competitive five years from now, the Five9 acquisition/merger was Zooms first attempt at trying to figure this out.
Even if Zoom's average usage per paid user goes down post-pandemic, it's revenue will remain constant and could still grow as new employees are hired and new companies switch over.