A full chapter on zerizus describes it as the midda that enables all other good traits to bear fruit, since every good intention left unacted upon is lost — zerizus is what closes the gap between intention and deed.
לָכֵן תַּחֲשֹׁב שֶׁתַּעֲשֶׂה הַטּוֹב בְּכָל אֵיבָרֶיךָ וּבְכָל מַחְשְׁבוֹתֶיךָ, וְתִבְחַר מִכָּל אֵבָר וְאֵיבָר קְצָת קַלּוּת וּקְצָת כְּבֵדוּת, וְהַכֹּל לְשֵׁם שָׁמַיִם: תְּהֵא קַל לָשֶׁבֶת עִם חֲבֵרִים הַמִּתְחַבְּרִים לַתּוֹרָה וְלַמִּצְווֹת, וּתְהֵא כָּבֵד לָשֶׁבֶת עִם הַלֵּיצָנִים וְעוֹשִׂים רָעָה. וּתְהֵא קַל בְּעֵינֶיךָ לִרְאוֹת דָּת וָדִין וְעִנְיְנֵי הַמִּצְווֹת, וּתְהֵא כָּבֵד בְּעֵינֶיךָ לִרְאוֹת מַעֲשֵׂה הֲבָלִים, וּלְהִסְתַּכֵּל בְּאֵשֶׁת אִישׁ וּבַעֲבוֹדָה זָרָה. וּתְהֵא קַל בְּאָזְנֶיךָ לִשְׁמֹעַ מוּסָרִים וְתוֹכָחוֹת וְדִין תּוֹרָה, וּתְהֵא כָּבֵד בְּאָזְנֶיךָ לִשְׁמֹעַ נִבּוּל פֶּה וּדְבָרִים בְּטֵלִים. וּתְהֵא קַל בְּאַפְּךָ לִכְעֹס עַל הָרְשָׁעִים, וּתְהֵא כָּבֵד בְּאַפְּךָ לִכְעֹס עַל הַצַּדִּיקִים. וּתְהֵא כָּבֵד בְּפִיךָ וּבִלְשׁוֹנְךָ הַמְּרִיבוֹת, וְהַשְּׁקָרִים, וְהַלֵּצָנוּת, וְהַלָּשׁוֹן הָרַע, וּתְהֵא קַל בְּפִיךָ בְּדִבְרֵי תוֹרָה, וְתוֹכָחוֹת, וּלְצַוּוֹת עַל הַטּוֹב. וּתְהֵא כָּבֵד בְּיָדְךָ לְהָרִים יָד בְּרֵעֲךָ, וּתְהֵא קַל בְּיָדְךָ לִתֵּן צְדָקָה, וְלַעֲשׂוֹת מְלַאכְתְּךָ בֶּאֱמוּנָה. וּתְהֵא כָּבֵד בְּרַגְלֶיךָ לֵלֵךְ בְּדַרְכֵי הָרְשָׁעִים, לָלֶכֶת לְמִשְׁתָּאוֹת וְלָלֶכֶת בְּטִיּוּלִים, וּתְהֵא קַל בְּרַגְלֶיךָ לָרוּץ לְבָתֵּי כְּנֵסִיּוֹת וּלְבָתֵּי מִדְרָשׁוֹת, וְלָלֶכֶת לְבַקֵּר חוֹלִים, וְלַעֲשׂוֹת לְוָיָה, וּלְכָל הַמִּצְווֹת. וּתְהֵא כָּבֵד בִּלְבָבְךָ לַחְשֹׁב הִרְהוּרִים רָעִים, וּתְהֵא כָּבֵד עַל הַקִּנְאָה וְעַל הַשִּׂנְאָה, וּתְהֵא קַל בִּלְבָבְךָ לַחְשֹׁב הִרְהוּרֵי תּוֹרָה, וּלְהַשִּׂיג מַעֲלוֹת אַהֲבַת הַשֵּׁם יִתְבָּרַךְ וְיִרְאָתוֹ הַטְּהוֹרָה. וּבָזֶה תְּהֵא קַל וְזָרִיז בְּלִבְּךָ לְהִתְדַּבֵּק בָּאוֹר הָעֶלְיוֹן.
Therefore, you ought to think of doing good with all of your limbs and with all your thoughts and you should demand of every limb sometimes to be easy and sometimes hard, but all should be intended for the sake of Heaven. It should be easy for you to sit with companions joined together for the study of Torah and the commandments, and it should be hard for you to sit with scoffers and evil-doers. It should be easy for you to see law, justice and the commandments executed, and it should be hard for you to see frivolous deeds and to look upon idol-worship and immorality. It should be easy for you to hear words of rebuke and chastisement and the law of the Torah, and it should be hard for you to hear obscene and idle talk. It should be easy for you to be angry with the wicked, and it should be hard for you to be angry with the righteous. It should be hard for your mouth and your tongue to indulge in quarrels, falsehoods, scoffing and gossip, and it should be easy for your mouth to speak the words of the Torah and to censure when necessary and to tell people to follow the good. It should be hard for you to lift a hand against your friend, and it should be easy for you to give alms and to do your work faithfully. It should be hard for your feet to walk in the paths of the wicked, to go to drinking parties and to stroll about aimlessly, and it should be easy for your feet to run to the synagogues and the houses of study, to visit the sick, to escort the dead, and to perform all the commandments of the Torah. It should be hard for you to think wicked thoughts in your mind, and it should be hard for you to indulge in envy or hatred, but it should be easy for you to think thoughts of the Torah, and to attain lofty heights of love of the Lord, Blessed be He, and a pure reverence for God. In this manner, you will be quick and alert in your heart to cleave to the light sublime.