Zuma launch has indeed slipped to Saturday the 6th.
And may slip to Sunday the 7th. Today they apparently did a second Wet Dress Rehearsal. And it was still at the pad as of 4:30 PM. Time is tight to lower it, roll it back , add the payload, roll it back, and prepare for launch. So that adds to the speculation it may slip to Sunday.
Apparenttly the same beginning of launch window regardless, 8:00 PM EST.
Keep all this in mind when it comes to when FH launches. Rocket-wise, this is a simple routine launch, other than no info about the payload. And that speculated FH Static Firing on the 6th, just got blown out of the water, the 6th was soonest likely, after Zuma launching on the 4th. So a Zuma launch on the 7th, would likely put FH first static firing to the 9th/10th at the earliest. Theoretical FH launch on the 15th, likely pushed to at least the 18th/19th (and if that the static firing goes well, which apparently did not even go well with Zuma's booster for a simple WDR. Or that they'd only do one Static Firing, which would be surprising for FH's 27 engines, being stagger ignited two-at-a-time).
Some of those "apps" are nice but please don't post a launch date based on them, some suffer from GIGO syndrome. Go to SpaceflightNow or NasaSpaceFlight, or some highly reliable up-to-date source. Besides, having any idea of when FH will finally launch is more an exercise in reading Tea Leaves than anything else.
Here is NSF's thread on updating news on Falcon Heavy's first launch:
https://forum.nasaspaceflight.com/index.php?topic=44376.40
And the discussion thread for the vehicle, not the payload:
https://forum.nasaspaceflight.com/index.php?topic=42705.0
And the thread for the payload (Tesla Roadster)
https://forum.nasaspaceflight.com/index.php?topic=44375.0