I used my garmin footpod (that I also used on treadmill) on elliptical last year while injured. It did track the steps for sure. Will work for zwift.
Not sure how accurate it is though? There is a calibration factor that you can tweak to match to length of your steps. Ideally you want the steps from the footpod to match the distance spent on the treadmill and zwift I guess?

Do you recall the outrage that occurred the last time someone used the elliptical and considered it a run?! You are entering sharky waters! ;)

It's always going to be an inaccurate hack. The pod has no way of compensating for/knowing the difficulty setting on the elliptical; it reads the same for a workout done on level1 as one done on level10.

If you always worked out at the same level setting, you might be able to use HR and set the stride length on the pod so that the "speed" matches the speed you run on the treadmill at the same HR.

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ECMGN Therapy Silicon Valley:
Depression, Neurocognitive problems, Dementias (Testing and Evaluation), Trauma and PTSD, Traumatic Brain Injury (TBI)

The idea is to keep the elliptical at a resistance level that matches the effort of running on a flat terrain and have te pod providing speeds comparable to the effort level when running; for example: ~6'50"/mile for tempo run, ~7'30" for endurance etc.