Regarding the first question: it's NOT true that Zahn invented the planet, but is IS true that he invented the name for it:.
Coruscant chosen for the films
Regarding Coruscant appearing in the prequels, Timothy Zahn had this to say at Celebration III:
"Just to make it clear, I did not invent the planet…George Lucas had invented the planetwide city a long time ago. When I was starting the Thrawn Trilogy, they told me to coordinate with the West End Games source material, and they had it listed as the Imperial Planet. Well nobody names a planet 'Imperial Planet,' so I thought it needed a name, so I picked the word that means glittering: 'Coruscant.' Apparently, when it came time to choose a name [for the films], people persuaded George to go with Coruscant and be done with it. So I felt very vindicated -- the tail wagging the dog. It was an honor to be slipped into the movies this way.
For the second question, there are other examples (e.g. Aayla Secura), but I wasn't able to find a complete list.
From Lucas' statements in Starlog were commented on in a December 7, 2005 post on the starwars.com forums by Leland Chee, who maintains Lucas Licensing's continuity database (via SW Canon Wiki):
Chee: "GL is certainly not bound by the EU, though he's certainly open to using things created in it (Aayla Secura and the Coruscant name, for example). On the other hand, the quote you provide makes it sound like the EU is separate from George's vision of the Star Wars universe. It is not. The EU must follow certain tenets set by George through the films and other guidelines that he provides outside of the films."
Also, from Wookieepedia canon article, the following examples are shown (unsourced):
C-canon elements have been known to appear in the movies, thus making them G-canon; examples include the name "Coruscant," swoop bikes, Quinlan Vos, Aayla Secura, YT-2400 freighters and Action VI transports.
As an aside, from "philosophical" perspective, EU does NOT exist for Lucas:
Anything not in the current version of the films is irrelevant to Film only continuity. (Leland Chee post)