Hi, I have quite a lot of Zoeva brushes and to be honest I find them mixed. I bought a blending brush (eye) which I loved and ended up keeping for myself, and when I ordered another for my kit it was totally different when it arrived - the bristles on the first one were brown real hair, they were white and synethetic on the second one and a totally different texture. I checked and checked the descriptions and they are identical, same number printed on them and everything!
Overall, I prefer Sigma. I bought a set of Sigma eye brushes from their US website and they worked out just as cheap as Zoeva because I got them on flash sale with free international delivery. I didn't ever get charged customs duties or anything like that either. The handles are longer and the bristles feel nicer. I think Zoeva are okay, but I prefer Sigma and I probably won't buy Zoeva brushes again.
I have the Real techniques brushes for base and concealer too, and the Royal ones for powder and some eye ones - I think the Royal Silk range are better quality than Zoeva, personally.