The Yoga 300 is really more for editing text documents and viewing web pages. The graphics capabilities are pretty minimal on that so that is the primary issue, with ram and weaker ‘Celeron’ cpu being the 2nd and 3rd issues.
Despite all this, we do try and make our best effort to scale all the graphics features down on Zwift so we can still run on these types of machines. Other than making sure the machine is plugged into a wall outlet, there probably isn’t too much you can do to improve the performance. Buying faster ram to swap out what is in there might help a little, but it will never be a machine that generates totally smooth 3d graphics in Zwift - it’s just not built for that kind of thing.
PS, I see from our database that you are running at about 8 frames per second. That is far from optimal (30fps+ is where it’s nice and smooth), but it is usable if you can put up with the choppy graphics.