Help With Interleaved camera(s) effect

Hi guys,

I'm not sure if this should go here or not so please bare with me. I need to create an interleave image effect where I can mix camera outputs to a image effect, basically what I want is something like this:

Do you guys know more or less, or can guide me where to search/what to use to do this?, I was thinking that maybe the solution goes along the lines with using the stencil buffer but I'm not 100% sure about it :/

Thanks a lot guys