For Mac users - a new webcam app.
I'm adding this to existing 'webcam' questions for future searchers.
I am in no way affiliated with this product or the company making it - this is a simple user to user recommendation.
I just discovered this today, announced on DPReview a new product called Cascable Pro Webcam £40 [£30 for the first week to 24 July 2020]
Assuming you mean one of the Canon EF 70-200mm lenses with a Canon EF 2X extender and an EF→RF adapter, yes you may.
But honestly, depending upon which EF 70-200mm lens (there have been seven different EF 70-200mm "L" lenses released between 1995 and 2018) and which version of the three 2X extenders that have been released over time in the EF ...