You need to be able to reinforce Africa, and that means dealing with the Persian Mediterranean Fleet. Either by avoiding it and landing forces in the hinterlands, then marching troops to the scene of battle, or by defeating it.
The Persian Mediterranean Fleet, while numerically stronger than the Ottoman, is techlevel 12 crap. With the right investment, you could build a fleet capable of beating it. A few hundred galleys can likely do it, for instance, and even if they cannot but can only inflict a few casualties, it takes a long, long, time to build new hulls for the PMF. My one mediterranean shipyard and one port have a grand total capacity of...
four ships (yes, four!) at a time. The Ottoman Empire can recover from naval losses on the mediterranean much, much, faster than Persia.
The thing to remember is that you need enough troops to stop attacks of 120K-150K cold in their tracks, with the option of stopping (or at least delaying) attacks of twice that magnitude in both Anatolia and Africa at the same time so long as you are on the defensive. This is based on the Persian habit of raising about 140K/month in the Tabriz/Tabaristan/Isfahan CCs and sending them off bundled towards whatever front seems lacking during the first few months of a war, and then as necessary.
Be
exceedingly careful when crossing from Ottoman Anatolia to the Persian middle east. It is a crossing that inflicts heavy attrition, and Persia usually has a 50/80/0 army located in Syria in wartime ready to pounce.
And never, ever try to march south past the Persian Mountains of Doom without some 300K-400K soldiers unless you are sure Persia is already defeated.
You will know that you have turned the tide if my manpower runs out, and that you may be winning the war if I begin talking about using some of my eastern forces. I typically have 250K-300K tied down in Afghanistan and India at all times to discourage predatory thinking in colonial nations and to fight the occasional rebellion.
Basically, to win, you will need to bleed the Persian forces. You have an ally here -
me 
I like throwing armies around and don't mind casualties too much so long as they seem to further my overall aim; I have been known to sacrifice my armies for both fun and profit - and sometimes, my gambles don't pay off. Present me with a nice target during a war, and I am more than likely to go after it even when I am nearly certain that it must be a trap, believing that I can beat the trap anyhow or that the prize justifies the risk. A character flaw, and one that I am aware of, yet one that can be used against me nonetheless - and has been in the past.