With ZCO 7.2 , ZCO now respects the Outlook profile configuration about sync time. Please see :

"ZCO not automatically sync'ing - have to manually sync"
Bug 73440 – ZCO not automatically sync'ing - have to manually sync

Comment 5 from that bug states:

OL2010: Send/Receive ribbon -> Send/Receive Groups drop list -> Define Send/Receive Groups -> "Schedule an automatic send/Receive every"
OL2003+2007: On main toolbar Send/Receive drop list -> Send/Receive Settings-> Define Send/Receive Groups -> "Schedule an automatic send/Receive every"

A future change or option might also be available with the work behind this RFE:

"SNDRCV: ZCO sync should be governed by waitsets rather than polling"
Bug 61155 – SNDRCV: ZCO sync should be governed by waitsets rather than polling