If both flashes have sync voltages from about 60v to 200v then they should work fine together. If one is low voltage (5v or 12v) and one is high, I wouldn't connect them together.
I looked into the Cactus triggers. They use an opto triac which is rated at 400 volts. Probably the same component is used in modern cameras which are rated up to 250v but many paranoid people will not connect anything over 6v to.