1) do micro, againist mantis its very effective scince of its rate of fire and slow projectlie, moving a tank in circles would dodge likely 80% of its DPS, meanwhile cybran mantis is very bad for microing and mostly when you micro 10 tanks can beat 15 of mantis. If enemy tries to micro with mantis you can eat 25 of them
2) try using PD if he do not ever build arty, put near it 3-6 tanks with arty if he makes arty
3) get up def line and enough production and start ecoing till you have to produce atleast 4 iishavohs/1 cycle (9x4 = 36 mass)
or more if possible. You can contiunue spamming him with chickens even when have T3 mexes or make othuums, if enemy is still at T2 and he has no OC you can just target his com and he will explode. Dont care his army or eco if you are sure they will survive till the com explodes.