reserve p,p1,p2,q,r,F,G,G1,G2,H,H1,H2 for ZF-formula,
  x,x1,x2,y,y1,y2,z,z1,z2,s,t for Variable,
  a,X for set;

theorem
  All(x1,y1,z1,p1) = All(x2,y2,z2,p2) implies x1 = x2 & y1 = y2 & z1 =
  z2 & p1 = p2
proof
  assume
A1: All(x1,y1,z1,p1) = All(x2,y2,z2,p2);
  then All(y1,z1,p1) = All(y2,z2,p2) by ZF_LANG:3;
  hence thesis by A1,Th14,ZF_LANG:3;
end;
