I want to control the two upper fans in my N300 case with a Zalman Fan Mate 2 and I'm wondering if it is reliable to connect two fans (in my case two Sickleflow fans) in parallel. If it is, connect the Fan Mate 2 to the PSU and then connect a generic Y-splitter to have two regulated power outputs. If not possible, is there any alternative to control two fans with the same controller (I want it to work at the same speed approximately).
as long as the total power of the fans that you are trying to control is less then 6 watts, You will be fine.
You have two fans of the exact same model, so chances are that they will be running at (roughly) the same speed.
The only thing that won't work is the RPM reporting on the fan. the yellow cable is designed to be connected to one fan only.