Make sure you pair the Snap to Zwift with the FE-C option. I made the mistake of pairing it through the generic ANT+ initially and got loads of signal dropouts where the registered power would drop to zero for a couple of seconds every 5 minutes or so. Haven’t had a single one since I paired it as an FE-C device.
A USB extension cord that allows you to place a bit of distance between the ANT+ dongle and your computer will also help with reducing communication problems. Best signal will be obtained if the ANT+ is placed close to the trainer.
Once the Snap has been calibrated you don’t need to run the Wahoo app on your phone to use zwift. Daily calibration spindowns can be run directly through the pairing screen on Zwift by clicking the spanner icon (after first warming the trainer up by riding for about 10 minutes).