I'm wondering, is this Competitive? Because Landorus tears this Team apart.
Tyranitar; Earth Power or Focus Miss
Reuniclus; U-Turn or Earth Power
Forretress; Earth Power
Gliscor; Hidden Power [Ice]
Heatran; Earth Power
Assuming it uses those exact Moves, you're screwed. I'll help you out with this problem a little later on in this Rate.
Leftovers > Choice Scarf on Tyranitar, and Fire Blast > Pursuit to hit Ferrothorn and co.
Althought Gyro Ball is a solid STAB for Forretress, tbh Volt Switch is better for escaping Magnezone or just switching in an appropriate counter.
Substitute > Ice Fang on StallScor, it allows it to further stall things that it outspeeds, and neutral Earthquake does more than 2x SE Ice Fang.
Celebi just dosen't seem to do well with NP, as Scizor comes in, takes any of it's Attacks and can KO with Pursuit or U-turn, so I'd use 56 Hp / 252 SpA / 200 Spe to outspeed Mamoswine, and run Hidden Power [Ice] / Leaf Storm / Psychic / U-turn + Life Orb.
I'd honestly scrap Celebi however as it does little to help with the Landorus problem and Scizor is all over it, leaving your Team very weak to Rain Teams once Celebi is removed. To remedy this and help with the Landorus problem, I'd run Scarf Keldeo with Hidden Power [Bug] / Surf / Secret Sword / Icy Wind > Celebi, Keldeo fears no Moves from Scizor and can OHKO Landorus lacking an RP Boost. It also annihilates Celebi on the switch in with Hidden Power [Bug].
Hope this wall of text helps, haha.
Tell me how you feel? I feel like the grass is green