Yes, Zentrunk SIP trunks support SIP OPTIONS pings.
SIP OPTIONS pings are widely used as a health check mechanism in SIP communications networks. You can have your PBX issue SIP OPTIONS messages as a ping mechanism to a Zentrunk SIP trunk and Zentrunk will respond with an appropriate response.
SIP OPTIONS are supported only on sending requests to an outbound trunk URI and not to trunk IP addresses. We recommend not sending more than one SIP OPTIONS message every 10–15 seconds to avoid your requests getting blocked.