Hij is precies zo snel als het paard.... Hmmmm sounds a little odd to me.
Native Dutch would say 'hij is net zo snel als het paard' or 'even snel als het paard'.
Using 'precies' is like saying the guy is E-X-A-C-T-L-Y as fast as the horse, which would be a strange thing to say.
Best not to think about what he did for an encore.
There is a slight difference in usage. In this context, 'even' (not unlike its English counterpart) implies a state of equality. When comparing two things this means something that is 'even ... als' is 'just as ... as'.
'Zo ... als' = 'as ... as'. But, if you make it 'net zo ... als' its meaning is roughly the same again as that of 'even ... als'.
- Jij bent even groot als je vader = you are just a tall as your father
- Jij bent zo groot als je vader = you are as tall as your father
- Jij bent net zo groot als je vader = you are just as tall as your father
It's that simple. :-)