You appear to be making things more complicated than they should be.

To be clear, you have an Audio Video Receiver (AVR) with your Comcast Box hooked up to HDMI Input 1 of the AVR and a Laptop Computer hooked up to HDMI 2 of the AVR.

You want to be able to switch between HDMI 1 & HDMI 2, right? So, why not just create buttons to go directly to HDMI 1 & 2? There's really no need to bring up an "HDMI Selection Screen" then using the Left and/or Right buttons to get to your desired HDMI source when a single button press, using discrete commands, will do it more quickly.

As for the zoom function, you can then also create a Macro that, with a single button press, will send the commands: Zoom, Left, Right, Select, (or whatever the sequence happens to be) rather than having to do each one manually.

You can assign these macros to any button you wish. Perhaps a 2-sec hold of the the "1" button to get to HDMI 1 or the "2" for HDMI 2.

Or, if you are used to using the Left button, then perhaps a 2-sec hold of the Left button to toggle you between HDMI 1 & 2 (this would be a variable where if you are already on HDMI 1 it would send a discrete command to go to HDMI 2 and go to HDMI 1 if you are already on HDMI 2, etc.)

The zoom macro could then be a press and hold of the right button, if you'd like.

The possibilities are endless. Use your imagination. The less button presses you manually have to enter, the better, IMO.