Alright...some stats here on most 1.4 hatches currently sold in the UK...
Fiesta 1.4 Silver 3d 12.3 s 103 mph 78 bhp
Focus 1.4 Studio 3d 13.6 s 102 mph 78 bhp
C2 1.4i VTR 3d 11.8 s 105 mph 75 bhp
Punto 1.4 Sporting 3d 9.3 s 111 mph 95 bhp
Civic 1.4 i-Dsi S 5d 14.1 s 106 mph 80 bhp
Accent 1.4 Atlantic 3d 11.9 s 110 mph 96 bhp
207 1.4 VTi Cielo (95bhp) 3d 12.4 s 115 mph 93 bhp
Lupo 1.4 Sport 3d 9.7 s 116 mph 98 bhp
Corsa 1.4i 16V Club 3d 11.8 s 107 mph 88 bhp
Arosa 1.4 16V Sport 3d (1/00) 9.7 s 117 mph 100 bhp
Clio 1.4 16V Privilege 5d 10.9 s 114 mph 96 bhp
So it is infact the most powerful engine currently, but not the fastest due to its weight. If the weight were reduced roughly 150kg then i reckon it would pretty easily be the fastest 1.4 on the road. My assumption is based on the above stats...
So it is right to say its at the top of the range for speed when compared to other 1.4's, but its not the fastest.
There are quite a few biger engine cars that the ZR105 is faster than, for example the 1.8 Focus Zetec, most of the Hyundai range, quite a few actually. The only thing letting the ZR down is the weight.