I think the Axon does have CDMA support, but it won't work with Sprint. The 6x won't work either since it has no CDMA support.
https://community.zteusa.com/thread/14616
Since Sprint is CDMA, you're gonna have limited options.
Take a look at the Moto G series.
Here's a list of Android phones officially supported by Sprint.
Google Pixel
Google Pixel XL
Nexus 6 (32 & 64 GB – black/white)
Nexus 5 (16 & 32 GB – black/white/red)
Nexus 5X (all versions)
Nexus 6P (all versions)
HTC One A9 (Sprint Version only)
Motorola X Pure Edition (16, 32 & 64 GB – all colors)
Samsung Galaxy S7 Special Edition
Samsung Galaxy S7 edge Special Edition
Moto G4
Moto G4 Plus
Hope this helps.