Extremely unlikely for so many obvious reasons (like the fact that proto-Somalis could pronounce 7a as the letter exists in Somali language.Arabic words with Z ( a letter that doesn't exist in the Somali language) gets changed to an S for example Waziir --> Wasiir Ziyaara ---> Siyaaro Zaynab ---> SaynabBut to get back at the Xaar/حار 'hot' part somali does have a similar cognate which is huur 'heat', we probably just dropped the X/ح or they turned H/ه into X/ح.
Somali nationalism stops many of you to accept the truth that Semitic civilization whether from Arabia or the Ethiopian highlands has influenced us greatly and there's nothing wrong with it.