HTC and iPhone 7 are running different operating systems - Android and iOS. Therefore, you cannot expect HTC or Apple would develop an app or program that enables you to transfer data across platform. Although HTC does offer an HTC Sync Manager while Apple offers iTunes, they are developed to deal with their mobile devices only - they can't help you transfer data directly from HTC to iPhone. But you can sync data from HTC to computer first using HTC Sync Manager, and then transfer data from computer to iPhone with iTunes.
Here, I have another recommendation for you to transfer data from phone to phone directly. cFone Mobile Transfer, that can be used as both an HTC transfer tool and iTunes, can save your trouble and time. You can select data you need and transfer them between any mobile device, or backup to computer and restore to mobile phone easily.