I’m afraid I can’t help you with your specific problem as I am only a fellow user myself. However, as this is your first post I would just like to warn you to expect a long delay getting an answer through this forum or zwift support. When you do get an answer, I wouldn’t hold too much hope that it will fix your issue. Not trying to be a “downer” but just preparing you for a long wait. Happy to be proved wrong in this thread though!
What other software do you have running in the background? Could there be something eating up a bunch of memory? I know I sometimes have to remember to kill Creative Cloud and similar things before running Zwift.