G. H. Hardy, "A Mathematician's Apology":
Some hold that it is 'mental' and that in some sense we construct it, others that it is outside and independent of us. A man who could give a convincing account of mathematical reality would have solved very many of the most difficult problems of metaphysics. If he could include physical reality in his account, he would have solved them all.
In a first clause there is 'could', in a second 'would have'. Kind of a mixing, it should be either 'could have' in a first, or just 'would' in a second.
The only way I see it is that in would [have solved] the whole have solved stands for the verb (with a taste of the perfect aspect). But I have never read about it. It would mean that have belongs to either would or the verb: would have [solved], would [have solved].