If you really have to make unencrypted SIP call, you can add ";encryption=0" tag to the dial string.
- Start the Zoom meeting
- Go to Invite, Invite a Room System
- Select SIP, enter SIP address and append without space ";encryption=0" e.g. firstname.lastname@example.org;encryption=0
Prerequisite: You will need Room Connector subscription to make SIP or H323 calls.