Hi. I record the audio separately into my zoom and then use plural eyes to sync it up in adobe premiere for editing. I believe my settings are at 48/24bit on the zoom as wav files. I feel like the audio is VERY slightly off. It's hard to tell, but has it been proven whether or not you have to adjust one or the other to sync them properly?
Sometimes you can have sync issues when previewing video in the timeline of your NLE but once you export it then things are fine, so do that check first. I assume that Premiere does the same thing as Final Cut Pro in that once you bring the audio into your timeline it is transcoded to match whatever your sequence settings are (that's a FC term, may be different in Premiere, probably is in fact) so I don't know why you are experiencing audio drift.
I record my master audio on a Tascam DR100 and feed a line output to the 7D via a Beachtek DXA SLR. I found doing this the audio recorded on the camera was consistently 2 frames behind video. I attributed this to delay from Tascam output to Beachtek as recording with the mic directly into the camera didn't do this.
I just shift all audio, after PluralEyes 2 frames.
You can check this by recording a slate and seeing if the clap vision and audio link up. (Doesn't have to be a slate, just anything you can clearly see hear a clap and see the vision that caused it).