I suppose this really isn't a Lr thread, it's a Zenfolio thread.
I exported the same image to Zenfolio using both the full size image (4618x3121) and images reduced to Zenfolio's recommended 1550x850. I used a variety of Lr export sharpening settings. The best one is a reduced image set for high screen sharpening in the Lr export settings. The grouping is in the album http://homershannon.zenfolio.com/p965692660
I've attached a 1550x1000 jpg export that was exported with standard screen sharpening as a reference.
My Zenfolio contract is up in two weeks and I don't think I'm going to renew if this can't be worked out.