r52 <=> Zcom

How I can connect routerboard530+R52 to ZCOM XI-1500, which works in “PXP-mode”?

there seems nothing special about this device. is it configured as an AP or Client?

ZCOM Xi-1500 is based on Prism 2.0/2.5 chipset. It should work in WDS and Station mode. But bridge mode is not compatible with MT (Atheros based) I guess.