I agree. Even though the Zero has one analog nub, a lot of ps1 games like Xenogears, Tobal 2 (Japan import) or Ape Escape require dual-analog controls to play the game, etc.
Even IF there is a stable & working ps1 emulator one day for the Zero, I would only recommend playing games that use the left analog nub ONLY... like FF8, FF9 or Chrono Cross for instance.
Additionally, I am confident that there will be someone wise/intelligent enough to bring a ps1 emulator to life for the Zero one day... however, there will be drawbacks without the 2nd analog nub that, say, the PS Vita already offers. The PS Vita only costs $200... it's not THAT expensive when you think about it. I'm all about supporting the Zero, of course, but facts are facts... the ps1 era had NUMEROUS titles that implemented use of both analog controls... typically, the 2nd analog was enforced usually for camera angles... but, but... as many of you are already aware, many games used the 2nd analog control for additional interaction... again, like APE ESCAPE or TOBAL 2 (Jap. import), etc.
Also, the analog controls for the ps1 allowed a player to press them inwards for L3/R3 too... so, it's not that simple for someone to design a ps1 emulator for OpenDingux, make sure it's a stable release, & be compatible all around... it just isn't. A LOT OF WORK has to be invested in order to get it fully operational, etc.
I mean, I love the ps1 era of gaming... it's my 2nd favorite behind the 16-bit era... however, I am not gonna hold my breathe on a developer to release an emulator for the Zero within a yr or so because by that time, who knows?... maybe the GCW Zero 2 may be on the way or something better that has a clamshell design to mimic the 3ds or dual-analog nubs for games originally designed for the N64 and/or ps1, etc.
My final recommendation is just to get a PS Vita... personally, that's my plan soon. I also want a 'new' N3DS too... but all in due time.