My guess: That is simply too low spec to run Zwift.
The CPU is 9 years old.
When I began zwifting, I tried a few old PC. If the PC was too low spec, Zwift wouldn’t start.
The first PC that worked, was a Intel Quadcore Q8300 with a ATI HD5670 GPU.
Now I’m on a i5-3470 with a ATI HD7850