I need boy advice

I'm currently talking to one guy, and the other guy is my friend who wants to have sex with me. 

The guy I'm talking to (named Anas); we're both really into each other. A mutual friend introduced us a few months ago and we really hit it off. We're really close and we really enjoy each other's company. But we are NOT (yet) dating. TOMORROW, he is flying home to Saudi Arabia for the entire summer. We went on a date last night and we both agreed that this summer, we will both "do our own thing" and get back together when he comes home for school in the fall. 

My friend, Zach, and I are also pretty close. We originally met on tinder and for a little bit were really into each other, actually until I met Anas, and then friendzoned Zach. 

I have not had any sexual interaction in 5 months and I'm feeling really desperate. 

My issue here is morals, which I've never seemed to have many of anyways. 

Zach wants to have sex with me tonight. But I feel morally conflicted because Anas isn't even out of the country yet. 

What I'm asking is, What would you guys do in this situation???? 

Am I doing Anas kind of dirty by even considering having sex with Zach? 

[But keep in mind that Anas and I aren't dating (yet)]

****************************

UPDATE:

The sex was amazing, we cuddled all night. We both agreed we're just FWB, because he doesn't really want a relationship right now and I was honest with him telling him that I'm waiting for Anas. 

Thanks for your help and opinions, guys. 💜