That's a nice tall frame! I agree, looks like a Snyder frame, chain wheel especially. Forward facing dropouts without the elongated bracket for the fender braces doesn't seem like Snyder but maybe it's from when they switched from the rear facing dropouts.
2012 conversation from the CABE:
"Zenith was the name on the bikes sold by the Marshall Wells Hardware stores. The bikes were actually manufactured by someone else, often the Cleveland Welding Company. If you look at photos of Cleveland Welding bikes, you may find some that are the same as your Zenith. Cleveland Welding also made bikes for Montgomery Wards (Hawthorne), Gambles Hardware (Hiawatha), Western Auto (Western Flyer) and others. They sold them also under their own name badged as Roadmaster."
"Not to say that there aren't any but I have never seen a Cleveland Welding built Zenith. They probably did use more than one manufacturer to supply them with bicycles over time but the most common supplier seems to be H.P. Snyder who also supplied to Montgomery Ward and to D.P. Harris."