Zip vs Enumerate

[Jordan Wilson via Digitalmars-d-learn]

Hello,

Idiomatically, I make use of zip, however, when looking to speed 
up my program, notice that using enumerate leads to a 20-30% 
improvement:

void main(){
    auto x = iota(1_000).array;
    auto y = iota(1_000).array;

    auto func1() {
        return zip(x,y).map!(a => a[0]+a[1])
                       .array;
    }

    auto func2() {
        return x.enumerate
                .map!(a => a.value + y[a.index])
                .array;
    }

    assert(func1.equal(func2));

    import std.datetime.stopwatch;
    auto r = benchmark!(func1, func2)(10_000);
    // r[0] approx 1794 ms
    // r[1] approx 1295 ms
}

Is there anything I can do to improve zip, before I go ahead and 
change to the faster but slightly less readable enumerate? In my 
particular case, all ranges that I zip are of the same length, 
but not sure how I can leverage that information.

Thanks,

Jordan