Would it be safer to hard-code a static IP than a domain?

Ip's can (easily) be hijacked by nefarious BGP requests and offer no easy SSL. You could maybe add cert pinning to fix that, but it's quite inflexible.

Another added bonus of domains is the potential for subdomains to be used. This could be usful for many purposes: as load balancing/pooling mechanism (fictive example us4.zoom.us) and for compartmentalisation (api.zoom.us).