With few limitations, you can use almost any arbitrary combination of cameras and flashes. It is no problem to use a Nikon flash on the Zenit 122. The flash shoe and the functionality of the middle contact pin is standardized and supported by most camera and flash models. This pin is simply used by the camera to tell the flash when to trigger.

What will not work is any furth 'cooperation' between the camera and the flash like TTL metering or automatic transfer of film speed and aperture settings from the camera to the flash. I do however believe that all Nikon flashes have an A mode (automatic), in which the flash takes over the light metering without any support from the camera. This will work with the Zenit camera as well. You will have to set the film speed and aperture setting you are using on the camera manualy on the flash unit for this to work. You can of course also use the flash in manual mode, but that usually requires some quite tedious calculations.