Do you have 'Automatically adjust brightness' turned on?
It looks like your computer is near a window that has a lot of light coming into the room. As the weather changes fluctuations in that amount of light, I suspect the mac is adjusting automatically accordingly. Try turning that off and re-recording with QT Player.
As for the audio, the Zoom recorders can record at extremely high sample rates, as well as a variety of sample rates. The sample rates you use need to match the project sample rate or you may get timing issues. You could try to select the audio and use conform rate feature of FCPX. I believe these days that means selecting your audio clips and selecting Automatic Speed from the Retiming Options drop down at the lower left corner of the viewer. The biggest problems usually seem to occur between a 48kHz Project setting and 44.1kHz audio (or vice versa.)
If that doesn't work, then if memory serves (it's been awhile) I believe I had been able to correct the sync problem by loading the audio in Logic and exporting at the slower sample rate (e.g.: converting a 96kHz audio down to 48kHz). I do not know *why* Logic can handle the sample rate mismatches and FCPX cannot... but... there you go. I see you use Cubase - try using that to convert your audio to the project sample rate in FCPX. There's also a method of manually conforming audio (assuming that the rate of sync drift is constant.) Let me know if it comes to that...
