Hello Picopr,
If your motherboard and case have enough open PCI slots, then yes. What I would do is dedicate the 960 to the display by connecting that GPU to the monitor, then dedicating the p4000 to rendering by going to the NVIDIA control panel, 3d settings, program settings, then in the dropdown select the program you want to use the p4000 for, then click the box that lets you select a GPU to use for that program, and select the p4000. Do this for every program you need it for and you should be set
Best of luck!