Based on breakdown of all info we can compile (which is a lot more then who finished each tasks first), breakdown of time for navigation, time to complete tasks, how much teams lost waiting for tasks to start (typical of really good teams).
For example in modern TAR its normal to get several episodes a cycle that don't feature bunching, basically giving the first team, a great chance to remain first (yet actually race much worse then other teams), season 16 had a great example of this with The Cops starting first (no bunching) and they finished first. But the time to complete was actually tied with the slowest team. And it just one of many, many examples,where the results dont actually highlight how well a team actually did.
Based off of this I would say its between Eric or COlin.
Zac managed to really drag his partner through, and that took a lot, but they never managed a strong game, and at that time, task wise Zach could do all the tasks pretty much, unlike later seasons where their was a division of labor. Still a great guy though.
And a lot of modern teams have things like legs with no equalizers, multiple artificial facets of the race to change order, and are done over shorter periods of time so that they shouldn't be ever as tired as teams that raced 13 full legs. THough in fairness its a lot easier to compare racers over certain seasons.
Easier to compare seasons 1 - 5 (fast forward every leg), seasons 6-11 (full 13 leg seasons, and tasks that each person must accomplish), seasons 12- to current (U-Turns, and various other tasks to mix up the order, more episodes that have no equalizers, ect).