You can do that but would it be safe or would such installation be approved by your local jurisdiction code enforcement division? That I can’t answer. There are also a couple of important variables;
Where / how is that oval pipe installed?
Is it exposed (its entire run) for evaluation to ensure it is in a good condition or concealed inside walls.
If it runs inside the wall cavities and there’s no way of knowing about the oval vent pipe condition (maybe corroded, holes in its surface) I don’t believe such installation would be approved by any inspectors.