I would be surprised if there were any synergism between clomid and nolva.
Clomid is a "racemic' mixture of two isomers of a compound, enclomiphene and zuclomiphene, whereas nolva consists of the single isomer enclomiphene.
Enclomiphene is an antiestrogen, while zuclomiphene is estrogenic. The body metabolizes both isomers into compounds that have even greater affinities (100 fold) for the estrogen receptor.
The body also has enzymes called isomerases that can convert the metabolites back and forth into each other. So no matter which drug one takes, there will always be a combination of estrogens and antiestrogens in the circulation.
One study found that 20mg of nolvadex was equivalent to 150mg of clomid in raising LH levels in men. (1)
(1)Fertil Steril 1978 Mar;29(3):320-7 ,
Hormonal effects of an antiestrogen, tamoxifen, in normal and oligospermic men.
Vermeulen A, Comhaire F.