How to cmd-tab to a group of windows, from different programs? I am writing a LaTex document in a Terminal text editor, which is automagically rendered as a pdf in a Zathura window (which is drawn by XQuartz). Each window occupies half the screen.

I would like to be able to ⌘-tab between a maximized Firefox window and that pair of windows. Can this be done? 

If this could be done if it weren't for the XQuartz rendering, I could switch to Skim (with a regular macOS window). I own BetterTouchTool and Alfred, if either might be useful in a way I have not thought of.
You can achieve this by using multiple desktops on your Mac. 

Start off by going into mission control (either swipe up with 4 fingers on your trackpad or press the f3 key) and then move your cursor to the top left of the screen and press the plus button. Drag the windows you want over to the new desktop then click on the new desktop and arrange the windows. You can quickly switch between desktops with cmd and he left or right arrow.