Hi Emotofreak-
We are just getting started on all 3 of these integrating as well. We are going to be using free software from this website to integrate QB and Zen Cart. libermansound.com/qbi . I can't comment yet on how well it's working, as we're still installing it and haven't been able to test it.
I don't yet have an answer for the salesforce part. Have you had any more luck getting an answer on this?
I see your post is relatively new, but, I'd love to hear if you have any more news and perhaps keep in touch about this....
My husband is a moto freak, what's your biz?
Thanks,
amie