User:AxelBoldt/test

So:

${\begin{array}{ccc}\operatorname {Hom} _{C}(FY',X)&{\xrightarrow {\Phi _{Y',X}}}&\operatorname {Hom} _{D}(Y',GX)\\\\\downarrow {\scriptstyle \operatorname {Hom} _{C}(Fg,f)}&&\downarrow {\scriptstyle \operatorname {Hom} _{D}(g,Gf)}\\\\\operatorname {Hom} _{C}(FY,X')&{\xrightarrow {\Phi _{Y,X'}}}&\operatorname {Hom} _{D}(Y,GX')\\\end{array}}$