The VY had a series of grilles and they do not interchange.
The grilles were: Exec and Acclaim
Berlina
Calais
S and SS
There might be detail differences between them but generally each of the groups above are different dimensions and will not swap over readily. Series 2 models mucked around with them in details again, but the interchangeability issues remained.
VZ grilles don't fit VY's. Same probs - dimensionally quite different.