Relevant text:
10.4 Customer License Grant. You agree to grant and hereby grant Zoom a perpetual, worldwide, non-exclusive, royalty-free, sublicensable, and transferable license and all other rights required or necessary to redistribute, publish, import, access, use, store, transmit, review, disclose, preserve, extract, modify, reproduce, share, use, display, copy, distribute, translate, transcribe, create derivative works, and process Customer Content and to perform all acts with respect to the Customer Content: (i) as may be necessary for Zoom to provide the Services to you, including to support the Services; (ii) for the purpose of product and service development, marketing, analytics, quality assurance, machine learning, artificial intelligence, training, testing, improvement of the Services, Software, or Zoom’s other products, services, and software, or any combination thereof; and (iii) for any other purpose relating to any use or other act permitted in accordance with Section 10.3. If you have any Proprietary Rights in or to Service Generated Data or Aggregated Anonymous Data, you hereby grant Zoom a perpetual, irrevocable, worldwide, non-exclusive, royalty-free, sublicensable, and transferable license and all other rights required or necessary to enable Zoom to exercise its rights pertaining to Service Generated Data and Aggregated Anonymous Data, as the case may be, in accordance with this Agreement.
It never is by default. In fact, they got in a bit of a fiasco early on (before their current E2EE implementation) for using the term “end to end encrypted” after it was revealed they were simply referring to TLS.