which are you best at?
Both will get the money...and all things equal Zen will win a little more...but is your Red 7 much better than your Zen...can you repeatedly count down a deck without error for one but not the other? Are you much faster at Red 7 than Zen.
If you are downtown I would suspect you are there to play the single and double deck games...Zen would probably be better as it's play eff. is higher than Red 7. However, I suspect you may not be very experienced at counting yet, and I would say that using Red 7 is a good count anytime with any game, and especially for someone just starting out. Indeed, if this is your first time out, just playing basic strategy is a learning experience.
With a bankroll of $5000 you could go to the strip and play the shoe games, and Red 7 would be better there, its easier to play for long periods of time.
Whichever you game select, I urge you to have a plan for how much would will bet on each count, buy in for only a small portion of your bankroll (say 2 or 3 maximum bets--you can always buy in for more if you need to--casinos like to see you doing that) and limit you play to 1 hour or less in that casino during one 8 hour period.
Good luck and have fun.