The Yongnuo YN560-TX II has a radio transmitter made to communicate with Yongnuo manual flashes with built in radio receivers that use the YN560/RF605/RF603 protocol.
Your SB900 has an optical receiver for Nikon's CLS/AWLCLS/AWL wireless flash protocol.
Although the Yongnuo YN560/RF605/RF603 manual protocol and the YN622 TTL protocols are mostly incompatible, YN622 devices made since the end of 2014 can be set to receive YN560-TX signals to control manual flash power and manual zoom head settings as well as fire the flash. If you set a YN622N II to 'YN560 Rx' mode and attach it to your SB900 it should allow you to control the power and zoom head setting manually from the YN560N-TX attached to your camera and fire the flash in sync.