I wanted a Zestar when I was considering my tree purchases this winter. But I knew it was a pollination group 1 bloomer, so that's one of the reasons I ordered the Alkmene, which blooms in group 2. I have other group 2 trees, but they are in the back orchard, and the Z was being planted in the lower orchard.
I got all this info on orangepippintrees.com
BTW, yer WP belongs to group 2, so it should be blooming close to the same time as the Zestar. But, that info's on a web site, and the real world may be a different story.