"grumble grumble, stupid passive aggressive tactic.."
It's ok Volco, we can persevere. Start off with a Flame Burst to hopefully deal some more super effective damage, then use your rare speed advantage to Dig before you can be hit with another Mud Slap. We may miss on the way back up but at least your accuracy won't get even lower. That Endeavour could do some damage to us if we hurt him too much, so end with a simple Yawn."
Flame Burst > Dig > Yawn