The POD HD might work as MIDI Slave, e.g. concerning tempo based FX. If you set values as a note (score) value (1/2, 1/4, 1/8, dotted 1/4, ....) instead of fixed time values, it should take the sync. Take care of the GLOBAL / PRESET BPM value.

Please see also manual on chapter 2.10 - 2.11, PAGE 6 MIDI / TEMPO OPTIONS..

Sorry, I first misunderstood:

(The manual on chapter 5.9, PAGE 5, SETUP: DIGITAL OUTPUT SETUP says:

"When connecting to another digital device, it is best to clock the external device to follow POD HD Pro (with POD HD Pro as the "master" device) to maintain proper synchronization - please see your digital device's documentation for its digital clock features."

HD Pro = MASTER; other device = SLAVE.

If the other device cannot be set to SLAVE (follow POD HD Pro), no proper synchronization is guaranteed.)