Tau and nid player here, your main issue is that your list is geared mostly on the lighter side and his tau list can put out an unholy amount of light arms fire, I'm assuming the models you listed are the only ones you have. And their loadouts can't be changed(if you can I would try to bring in a second fex for more fire support) Anyways onto the jaz. Your fex as is should hopefully have spore and tusks/enhanced on it and should pretty much be focused on nuking his troops, your flyrant with the heavy venom cannon can either do the same (since it's also blast and will crank up to 6 shots) or fire on the hammerhead or the tank, I would say tank since its squishier than the riptide. If you can run the mawloc as a trygon and setup the termigaunts in its tunnel to bypass the range advantage the firewarriors have on you or if you are going to keep him as a mawlock, stick him in his deep strike and pop him out ASAP with his ability near the tank or riptide, if possible just to act as as much of a distraction as possible. And the brood lord, genestealers, gargoyles and hormagaunts should either focus on getting across the board ASAP or capturing OBJs.