iPad USB-C adapter to TV question

Hi All,
Hoping Simeone can help.
I have previously connected my iPad to and old big screen TV in the garage via a lightning to VGA adapter. It worked perfectly.
I have now bought a new iPad with a USB-C connection, bought a USB-C to HDMI cable, but can only get a small boxy picture with Zwift. If I put a video (Netflix) on it changes to full screen. Any suggestions from the technical gurus out there? How to I get Zwift to project full screen? Should I just go and buy a USB-C to VGA cable ?