Cold hardy Citrus refers to the pipe dream of crossing Trifoliate Poncitus with any other relation and develop a fruit to grow in temperate zones as cold as Zone 6.
This is a Trifoliate growing at my neighbor in Washington DC
This is the fruit from that tree 
What does that fruit taste like?
Don’t get me wrong the fruit is very redeemable. After picking if you let them sit on the counter for a week or two they will develop a bit of juiceable pulp. The flavor will mellow and 1 fruit as an addition to a pitcher of lemon aid will give you a flavor quite similar to Filipino Calamasi Orange Calamansi - Wikipedia
So crossing a Zone 5 Trifoliate with a Zone 9 is bound to get you a Zone 8 fruit right. No the cold hardness is lost in 1 or 2 generations and the Pine flavor never goes away. Lay sigh and whoo. Cold Hardy Citrus is a pipe dream a red mercury and anyone that tells you otherwise is a fool.
This is my Cold hardy Citrumelo I purchased from Logee’s 
As you can see from the photo that is clearly not doctored or anything and if of course using a person with normal size not very small hands. Citrumelo clearly displays its Trifoliate heritage and will absolutly grow in Zone 7
What do you mean the Kool-Aid is ready. Kool-Aid always gets a bad rep it was actualy Flavor-aid those cheep bastards.