You get Jax the bartender by asking for a drink and saying surprise me then keep saying you insist you'll pay for everything. To get Zenith, basically say what you want then start saying you actually don't want to have sex and then obviously hit yes to keep his number (why is there an option to throw it away).

how do u get dustin im still stuck there
i dont think ive managed it once lol

for Zeniths dating path you just need to talk to him on the second floor, once him and rose ask you to do the do with them you have to decline, then you have to stop Zenith from leaving, either console him or use humor after that you'll get his number. For Jax you have to ask for a drink, once at the option to chose select 'Surprise me!' once you pay for the drink refuse to accept change and offer the leftover money as a tip then he should slip you his number, if that doesn't work try small talking with him. Hope this helps friend!