I agree with Lauta_hibrid that purely zygotic varieties are the best starting point for anybody who wants a high percentage of zygotic seeds. The downside of such a choice is, however, that you have a very limited genetic pool for starting any breeding. It depends on the very special goals one has if that is a real downside.
As far as I know all oranges are mutations of a single ancient cross (Pumelo x Mandarine) x Mandarine. (I do not know what was father or mother.) On the one chromosome set oranges are pure mandarines, the second chromosome set consists of about 50% pumelo genes and about 50% mandarine genes. Oranges produce mostly nucellar seedlings. But there have been orange hybrids that are zygotic, namely: Sanford Citrange, Phelps Citrange, Clementine and Kijomi. There are also orange hybrids with a noteworthy percentage of zygotic seeds as C35. I conclude from that that all oranges are heterozygous for nucellar embryony. I would also assume that some citranges are only highly nucellar because of the Poncirus part of the cross.
Aside from these considerations, I would recommend to anybody who wants to make crossbreeding that he does not focus too much on the issue of nucellar embryony. I cannot boast to be a successfull breeder because most of my seedlings have not yet flowered. But I have produced a greater number of hybrids. So I can already tell from experience: Polyembryony and nucellar embryony are annoying but no real hindrance in many cases. If you believe that a certain plant has all the properties a good motherplant should have except zygotic seedlings then just try the cross. You may be surprised how many zygotic seeds you get! Or you may be disappointed. Then try it again with more flowers in more years. You will be likely to succeed. And when you succeed you will be faster as the one who waits the same time for getting a zygotic motherplant.
Today I harvested all my Yuzu fruits (very tasty by the way). Some had been pollinated by Dunstan Citrumelo. And surprise! About 1/4 of the seeds were green, the rest pale. That means that about 1/4 of all seeds must be hybrids and that an unknown number of the pale seeds must also be hybrids by the law of probability. (The green color comes from the citrus part of Dunstan Citrumelo, the pale color comes from Yuzu or the Poncirus part of Dunstan Citrumelo.) Ok, last year, I pollinated with Poncirus and had no hybrids at all, only nucellar seedlings. Does that matter? Only a year later my largely nucellar Yuzu gives my plenty of hybrids from a different but very interesting cross.
I got hybrids from 100% nucellar Calamondin, from 100% nucellar Tavares Limequat, from nucellar Vainiglia Sanguigno (very difficult though), from highly nucellar Dunstan Citrumelo, from Poncirus (nucellar seedlings unknown). Great, isn't it? But when I started my experiments I was so keen on getting zygotic mother plants. I was happy when I got Chandler. "Wow", I said to myself, "so many seeds in a fruit and all zygotic!" Yes, in theory. But I tell you something: Although my Chandler is full of flowers every year I got only one single fruit with seeds in it. All crosses were in vain except the one with "African Shadock x Poncirus". Poncirus pollen on Chandler - all in vain. Other pollen? All in vain. But Chandler pollen on allegedly nucellar Poncirus: one hybrid! I do not know what the problem with my Chandler is. Others were more successfull. But one thing I do know: There is a great difference between theory and practise. The good news is: Although the practise may laugh at your best theories, often it is more friendly to you than all earnest considerations.