The L series diesel engine found in the ZS, is easily tuned for a reliable 150bhp+
This is basically from fitting injectors from the older L series engine, found in the older bubble shaped cars i.e Rover 200/400/600, followed up by a re-map.
Injectors are approx £50+, and i can do re-maps for £220 here in peterborough.
Plenty of smiles per gallon with the ol' L series derv
Cheers
Dave