apply IsDeduct.mp_ (eq_ z z)
case h1.h1.h1
x y z : VarName
⊢ IsDeduct ∅ (((eq_ x y).and_ (eq_ y z)).imp_ (eq_ x z))
case h1.h1.h1.a
x y z : VarName
⊢ IsDeduct ∅ ((eq_ z z).imp_ (((eq_ x y).and_ (eq_ y z)).imp_ (eq_ x z)))

case h1.h1.h1.a
x y z : VarName
⊢ IsDeduct ∅ (eq_ z z)