I have contacted support a few months back regarding terrible performance caused by severe latency. After looking at my logs, support told me there was nothing that could be done about it, at least until they roll out additional servers.
Now at some point in time i started using bluetooth wireless headphones, as they paired with the PC the audio always lagged behind. I did some research regarding audio latency issues, this is when i stumbled upon the answer to both problems.
"The problem you guys are running into is a new Windows 7 “feature”.
To accurately measure time in a Windows PC, software uses the QueryPerformanceCounter function. Many applications, especially games, depend on this Windows function to accurately calculate FPS as well as for many other timing purposes in game including sound.
The problem is that for many computers, this function in Windows 7 is now based on the clock speed of the processor. If you overclock in the bios and then boot up, this timer is calibrated and will work 100% correctly. If you use SetFSB or a similar program and you change the bus speed from within Windows, you have now just screwed up this very important timing mechanism. The number of applications that can choke after you do this is surprising, especially games."
That was exactly my problem, when i switched off that windows “feature” everything went back to normal. I hope the Zwift support team will take this info into account next time they are faced with a bad latency ticket and improves someone’s experience in zwift!