zenmarket seems like shoppingmalljapan, ie. deposit prior to purchase.
i want to give ZM a try, but based on my experience with SMJ, i have some reservations about the deposit mechanic, specifically about getting it back after a failed bid/purchase.
when you make a deposit, you lose about 1-2% on the forex conversion (and another 1-3% if your CC or bank charges a foreign transaction fee). but the forex loss is fine, since you would incur this anyway with any foreign purchase that isn't denominated in your home currency.
the problem is that when the deposit is refunded, the likes of ZM and SMJ will likely refund the yen amount they received ( which is already net of the 1-2% extra you already paid upon making the deposit) and that yen refund will incur another 1-2% loss when it's converted back to your home currency. this can of course be avoided by simply keeping the deposit with ZM and using it for future purchases. this works out fine if you make frequent purchases and the deposit balance is small. but a failed bid on a 100,000 yen auction might still take a while to consume.
ZM says they use STRIPE, which is 2% on forex conversion. Mastercard and Visa are typically 1.xx%. per ZM, deposits via CC will use STRIPE rates.
if you use Paypal for the deposit, Paypal can auto-convert to yen, but Paypal forex rates are worse than CC, and likely worse than STRIPE. so the workaround is to make a yen denominated deposit via Paypal but turn off the Paypal auto-conversion and use CC conversion instead. however, when the deposit is refunded (and it will be refunded in yen), Paypal gets to apply their worse forex rates on the back conversion.
ZM's payment fee (3.35%) is essentially the same nature as other proxies' commission/service fees. they just attached it to deposit payments rather than to the purchase transactions. other proxies do this as well, so they can claim they only charge a minimal flat fee on purchases.
still, ZM's 3.35% + 300 yen is a very good rate, and better than buyee's 5% + 200 yen. at least for YAJ purchases >5,000 yen.
what is hard to beat is that amazon and rakuten purchases via buyee are 0% service fee.
on the other hand ZM's free consolidation beats buyee's 1000 yen consolidation fee.
what i noticed in my consolidated packages of YAJ purchases, is that most YAJ sellers use very light packing materials when shipping domestically. some are in paper bags/mailing envelopes, or the item box is just covered with bubblewrap and thick paper. so the increase in size/weight of the consolidated shipment due to domestic shipping boxes has not been much of an issue for me. for sure, they can be consolidated more efficiently if the items were unpacked then repacked, but YMMV if the final box will be materially smaller and lighter.
for amazon and rakuten purchases, i place multiple items into a big order, and from as few sellers as possible. this way, my purchases are already pre-consolidated (for free) into as few boxes as possible before they're sent to the buyee warehouse. often, they are already sufficiently consolidated and big enough by themselves that i don't bother having buyee consolidate them further and just have them shipped out on their own.
i guess for me, i will try out ZM only for high-value "buy it now" items on YAJ, so i won't have to deal with deposit refunds and/or maintaining a balance.