
Eu quero usar Chapterstyle Thatcher para as partes e Chapterstyle Veelo para o resto (capítulos, etc.).
MMWE:
\documentclass[10pt,a4paper,openany]{memoir}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[german]{babel}
\usepackage[left=2.00cm, right=2.00cm, top=2.00cm, bottom=2.00cm]{geometry}
\chapterstyle{veelo} %-----------------------------> This for chapter etc
%part
\aliaspagestyle{part}{empty}
\usepackage{fmtcount}
\chapterstyle{thatcher}%-----------------------------------> This for parts ONLY
\renewcommand*{\thepart}{\arabic{part}}
\renewcommand*{\parttitlefont}{\normalfont\large\MakeUppercase}
\renewcommand*{\partnamefont}{\normalfont\scshape\MakeLowercase}
\renewcommand*{\partnumfont}{\normalfont\scshape\MakeLowercase}
\renewcommand*{\printpartname}{\partnamefont{\ordinalstring{part}[m] part}}
\renewcommand*{\printpartnum}{}
\renewcommand{\midpartskip}{\par\parbox{0.5in}{\hrulefill}\par}
\renewcommand{\beforepartskip}{\vspace*{\fill}}
\renewcommand{\afterpartskip}{\vspace*{\fill}}
\renewcommand*{\cftpartname}{Part}
\renewcommand*{\cftpartpresnum}{\space}
\renewcommand*{\cftpartaftersnum}{.}
\renewcommand*{\cftpartaftersnumb}{\space}
\begin{document}
\part{Love}
\chapter{Help}
\part{Is}
\chapter{Help}
\part{The}
\chapter{Help}
\part{Air}
\chapter{Help}
\end{document}
Como está até agora:https://docdro.id/cPVVpH8
Resumindo: faça o estilo de capítulo veelo para os capítulos.
Responder1
Fiz algumas pequenas alterações no seu MWE para lhe dar o que você deseja.
% memchapprob.tex SE 535653 different chapter styles
\documentclass[10pt,a4paper,openany]{memoir}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[german]{babel}
\usepackage[left=2.00cm, right=2.00cm, top=2.00cm, bottom=2.00cm]{geometry}
\usepackage{graphicx} % needed for the veelo chapterstyle
\chapterstyle{veelo} %-----------------------------> This for chapter etc
%part
\aliaspagestyle{part}{empty}
\usepackage{fmtcount}
%\chapterstyle{thatcher}%-----------------------------------> This for parts ONLY
% you have basically redefined \part to give this
\renewcommand*{\thepart}{\arabic{part}}
\renewcommand*{\parttitlefont}{\normalfont\large\MakeUppercase}
\renewcommand*{\partnamefont}{\normalfont\scshape\MakeLowercase}
\renewcommand*{\partnumfont}{\normalfont\scshape\MakeLowercase}
\renewcommand*{\printpartname}{\partnamefont{\ordinalstring{part}[m] part}}
\renewcommand*{\printpartnum}{}
\renewcommand{\midpartskip}{\par\parbox{0.5in}{\hrulefill}\par}
\renewcommand{\beforepartskip}{\vspace*{\fill}}
\renewcommand{\afterpartskip}{\vspace*{\fill}}
\renewcommand*{\cftpartname}{Part}
\renewcommand*{\cftpartpresnum}{\space}
\renewcommand*{\cftpartaftersnum}{.}
\renewcommand*{\cftpartaftersnumb}{\space}
\begin{document}
\part{Love}
\chapter{Help}
\part{Is}
\chapter{Help}
\part{The}
\chapter{Help}
\part{Air}
\chapter{Help}
\end{document}
Basicamente você redefiniu \part
para ter o estilo thatcher, então não há necessidade \chapterstyle{thatcher}
apenas de \chapterstyle{veelo}
. Mas, como indicado no manual, você precisa do graphicx
pacote, caso contrário, ocorrerá erros comveelo